A novel 2-bit PDAC based on quadrature phase modulation and differential demodulation together with balanced detection is proposed and experimentally demonstrated at sampling rates of 2.5GS/s and 10GS/s. The simulation results of expanded 4-bit PDAC from the 2-bit PDAC unit by using two channels of incoherent light with different wavelength are presented. This PDAC scheme is simple, compact and effective with high expansibility. Compared with other approaches, this method's output signal has a greater dynamic range and a higher noise margin.

In this report, we experimentally demonstrate efficient optical 3R regeneration of 40-Gb/s degraded data signals by using two schemes. The first 3R regenerator incorporates a dual-ring injection mode-locked fiber ring laser as the clock recovery module and an electro-absorption modulator (EAM) as the decision gate and the other 3R regenerator consists of an amplified feedback laser (AFL) for all-clock recovery and a semiconductor optical amplifier delayed interferometer (SOA-DI)as the optical decision gate. Optical clock with low timing jitter and uniform amplitude are successfully extracted with the use of the clock recovery units and significant improvement of the signal quality are obtained from 40-Gb/s RZ data signals degraded by polarization mode dispersion(PMD), chromatic dispersion or noise of amplified spontaneous emission (ASE).

The interaction of fiber dispersion and nonlinearities enable optimal regimes of operation of amplified optical communication systems that use XFP transceivers. System performance is described using OSNR tolerances for OC-192 and OTU2 modulated signals. An improvement in OSNR of 3-dB is achieved when allowing approximately -500ps/nm residual dispersion in the link which enabled about 45dB link budget.

The orthogonality of Mode Division Multiplexing (MDM) with Wavelength division multiplexing (WDM) and Polarization Division Multiplexing (PDM) is investigated applying WDM and PDM transmission over the LP₁₁ mode in a few-moded fiber. Two wavelengths, each carrying 10Gbit/s signals in two orthogonal polarizations are successfully transmitted with the LP₁₁ mode in a 10km long 2-mode fiber, resulting in a total 40Gbit/s data rate for one LP mode. This experiment demonstrates that MDM is orthogonal with WDM and PDM and can be regarded as a new additional dimension to increase optical networks' capacity.

We provide a closed-form expression for differential phase error variance in coherent systems. Based on the closed-form expression, a novel method of laser linewidth characterization and monitoring is verified by both simulation and experiments.

We investigate the nonlinear tolerance of coherent detected 50 Gbit/s dual-polarization binary-phase-shift-keying (DPBPSK), 100 Gbit/s dual-polarization quaternary-phase-shift-keying (DP-QPSK), and 200 Gbit/s dual-polarization 16-ary quadrature amplitude modulation (DP-16-QAM) for single carrier with pulse shaping and orthogonal frequency division multiplexing (OFDM). The performance of these systems is compared and tested in two different scenarios: dispersion managed and unmanaged links. The results show that employing return-to-zero with 50 % of duty cycle (RZ50) as pulse shaping has a superior performance, especially in dispersion unmanaged links.

We propose and demonstrate a 2 × 2 multiple-input multiple-output (MIMO) wireless over fiber transmission system. Seamless translation of two orthogonal frequency division multiplexing (OFDM) signals on dual optical polarization states into wireless MIMO transmission at 795.5 Mbit/s net data rate is enabled by using digital training-based channel estimation. A net spectral efficiency of 2.55 bit/s/Hz is achieved.

19Gb/s transmission over 23-km SMF is demonstrated based on 1-GHz bandwidth limited RSOAs with adaptively modulated optical OFDM. A novel baseband transmission technique with in-phase/quadrature channel separation is applied to halve the sampling speed requirements. Selective bit allocation with pre-emphasis and post compensation are used to optimize the transmission performance.

A precoding technology with a digital signal processor and high-speed DACs is a promising key enabler for realizing next-generation higher-order modulation systems. Achievement of a DAC operating speed of 40 GS/s or beyond is a prerequisite for high-speed precoded transmission. In this paper, the application of and the trends in optical precoding technology are reviewed. A high-speed DAC for optical communications at 40 Gb/s and beyond is introduced. To achieve a DAC suitable for digital signal processor based high order modulation, an interleaved DAC and a high-speed multiplexer are key technologies.

A carrier phase recovery method for optical transmission format of 16-QAM constellations is presented. The method can also be used in coherent optical single carrier or OFDM (CO-OFDM) system to implement blind phase recovery with low computational cost. We apply this method in 112Gb/s 1040 km CO-OFDM transmission, and compare its performance to those using the fourth-power estimator. Experimental results obtained indicate that the proposed method significantly outperform the fourth-power estimator.

The paper presents a new pilot-aided scheme to measure quadrature imbalance between the I and Q branch caused by imperfection of dual-parallel Mach-Zehnder modulator in a CO-OFDM transmission system. The method can accurately calculate the imbalance, and we implement the compensation of quadrature imbalance in a 36G CO-OFDM Receiver with applying GSOP algorithm.

We propose a modified symbol timing synchronization algorithm for polarization division multiplexed (PDM) coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems. This method can significantly reduce the impacts of the platform phenomenon and the chromatic dispersion, when it is compared with the typical Schmidl&Cox algorithm. Simulation results with the compare between the typical algorithm and proposed method show that the latter has much better performance in optical fiber channel. 1-dB signal quality improvement is achieved for PDM CO-OFDM system at 112Gbit/s data rate over 500-km SSMF without dispersion compensation.

A modified phase recovery algorithm with overlap controlled adaptively used for squared 16-QAM is proposed, which is based on the 4^th-power algorithm and relieve the problem of block-size-choosing. By using this modified algorithm, 1.8MHz linewidth tolerance for 25G Baud 16-QAM is improved on traditional 4^th-power algorithm.

We investigate the interaction between linear and nonlinear compensation within back-propagation algorithm applied to next-generation 400-Gbps systems. A significant performance improvement is reported by taking into account the interaction of these two parts.

In this paper, we first provide analysis and discussion on the optimal symbol rate for long-haul transmission. In particular, the optimal subband bandwidth in a multi-band DFT-Spread OFDM (MB-DFT-S OFDM) system is studied. We then carry out numerical simulation of 107 Gb/s MB-DFT-S OFDM systems and find the optimal subband bandwidth is 3.5 GHz for dispersion un-compensated systems. We finally show experimental demonstration of the nonlinearity improvement of DFT-S-OFDM over conventional OFDM systems.

Novel methods on photonic generation of different pulse modulation formats for impulse radio ultra-wideband (IR-UWB) over fiber application is overviewed. A flexible, high-speed and power-efficient photonic on-off keying and binary phase shift keying modulated IR-UWB over fiber communication system is proposed and demonstrated. IR-UWB transmission over 20km fiber and 0.25m wireless link without any compensation is presented. The transmission performance for both modulation formats is evaluated and compared by measuring eye diagrams and the electrical spectra.

In this paper, two models for diffuse indoor cellular optical wireless communication (OWC) systems with and without a holographic light shaping diffuser (LSD) are presented. For both models, the power distribution, the impulse response of the channels and root mean square (RMS) delay are described and analyzed. We perform a computer simulation to compare the channel characteristics of the typical indoor cellular OWC systems with that employing the holographic LSD. The results show that the system with the holographic LSD provides a more uniform power distribution and a less RMS delay spread for the same divergence angles.

In this paper, we design an interleave-division-multiplexing (IDM) based multiple-input multiple-output (MIMO) free-space optics (FSO) communication system. The system overcomes problems harassing conventional optical MIMO systems such as restrictions of antenna number and high complexity in receiver. An iterative on-off keying (OOK) modulated IDM MIMO detection algorithm is developed. Expression of an upper bound of frame-error-rate (FER) is derived. In addition, we evaluate the BER performance of the proposed optical MIMO scheme in various FSO scenarios. Simulations confirm that the proposed scheme can effectively increase the feasibility of FSO communications over Gamma-Gamma turbulence-induced fading channels.

A simple and cost-effective technique to generate coherent optical multi-carriers by using cascaded phase modulators is proposed and investigated. A detailed theoretical analysis is presented. The phase and amplitude relation of RF signals on two concatenated phase modulators are investigated. Simulation results are in good agreement with the theoretical analysis, and the experimental performance of 22 subcarriers with amplitude difference of 5dB shows that this scheme is a promising technique for the coming Tb/s optical communication.

Current status and trends in various sectors of photonics industry in Mainland China are reviewed, which includes optical fiber communication, optical preform, fiber and cable, photonic devices and chips, LED illumination and display, and photovoltaics. Then, from the challenges and risks they are facing, critical importance of innovation is discussed. In the evolving Innovation Economy, the core competence of a company, an industry or a country is its innovation power and the capability to grab (and manage) talented people.

In this Paper we investigate the optimization of constellations for polarization-division multiplexed transmission in standard single-mode fiber systems and for space-division multiplexing in a multi-mode fiber system.

We propose and experimentally demonstrate the generation of various modulation formats using a directly modulated chirp-managed laser (CML), including phase-shaped binary transmission (PSBT), inverse-return-to-zero duobinary (IRZ-duobinary), Manchester-duobinary, return-to-zero differential phase shift keying (RZ-DPSK) and return-to-zero differential quadrature phase-shift-keying (RZ-DQPSK). The CML-based modulation formats improved dispersion tolerance and their corresponding transmitters have the features of compactness, low power consumption and costeffectiveness, which are desired in metro/access networks. System applications of such formats are also studied.

Coherent optical DFT-Spread OFDM is a promising technology, which not only includes the advantage of coherent optical OFDM, but also presents low PAPR value. We experimentally demonstrate 1.45-Tb/s single channel coherent optical DFT-Spread OFDM over 480-km SSMF transmission.

In this paper, we investigate the phase noise elimination employing an optical pilot carrier in the high speed coherent transmission system considering the equalization enhanced phase noise (EEPN). The numerical simulations are performed in a 28-Gsymbol/s quadrature phase shift keying (QPSK) coherent system with a polarization multiplexed pilot carrier. The carrier phase estimation is implemented by the one-tap normalized least mean square (NLMS) filter and the differential phase detection, respectively. Simulation results demonstrate that the application of the optical pilot carrier is very effective for the intrinsic laser phase noise cancellation, while is less efficient for the EEPN mitigation.

The proposed receiver, which is based on joint-decision MLSE (JD-MLSE), employs direct detection with conventional balanced differential detection to compensate chromatic dispersion (CD) impairment on phase shift keying (PSK). The receiver can reach a lower BER and has a higher CD tolerance than balanced differential detection with MLSE, demonstrated by simulation and experiment. Applied to a 10-Gb/s DPSK experimental system, this receiver can equalize 3800-ps/nm dispersion.

Thanks to coherent detection and digital signal processing (DSP), linear distortions such as chromatic dispersion (CD) and polarisation mode dispersion (PMD) can in principle be completely compensated for in high-speed optical transmission. And indeed, effective algorithms have been devised and extensively investigated that allow CD- and PMDresilient transmission of high-speed signals over long distances, leaving optical noise accumulation and non-linear impairments as the factors ultimately limiting reach. Considerable research has been dedicated in the last couple of years to devise methods to increase the non-linear tolerance of optical signals by means of digital signal processing. In this review paper, we present an overview of the most promising techniques, show some examples of their application and outline the status of research on this important topic.

A new wavelength division multiplexed-radio over fiber (WDM-RoF) access network scheme supporting the simultaneous transmission of a 1.25-Gb/s wired data as well as a 1.25-Gb/s wireless data is proposed in this paper. An optical carrier suppression effect and sideband routing using the multiplexing of arrayed waveguide grating (AWG) with 50-GHz channel spacing are utilized to generate a millimeter wave band carrier. These techniques make the proposed architecture transmit both a wired data and a wireless one at the same time. A reflective semiconductor optical amplifier (RSOA) is employed at both central office and base station so that this architecture is operated colorlessly. Error free transmissions (BER of 10^-9) of both downlink and uplink are achieved simultaneously.

A novel photonic technique of millimeter-wave (mm-wave) sub-carrier generation using optical parametric loop mirror (OPLM) and fiber Bragg grating (FBG) is proposed. Due to the four-wave mixing (FWM) effect and loop reflection characteristic in an OPLM, a carrier-suppressed modulation signal is able to generate two new harmonic components with six times frequency spacing of the modulation frequency and the initial two optical tones can be reflected back to the input port by the OPLM itself, which servers as the first order filtering. At the transmission port of the OPLM, a matching FBG will give further suppressing on the pump light. Finally, a millimeter-wave sub-carrier will be obtained after the FBG.

A frequency interleaved multiplexing DWDM-ROF system was designed to improve the optical spectrum efficiency. In this system, each gap between carrier and the sideband is fully utilized. In the proposed scheme, two chances of baseband signals and two carriers for wireless applications with a data rate of 2.5Gbit/s, other two chances of baseband signals for wired for applications. The signals are distributed over 50-km single-mode fiber without any compensation. Meanwhile we designed a novel demultiplexer based on Fiber Bragg Grating (FBG) for this system. The simulation experiment verified the feasibility of the proposed method, and also showed good ability to resist the channel crosstalk.

This paper has proposed a radio-over-fiber (RoF) link carrying two 10Gb/s 16-QAM mm- wave signal streams. Since the dual-tone 40GHz optical mm-wave are generated by frequency quadrupling via a LiNbO3 modulator and the two QAM signal streams are modulated on each tone by single sideband (SSB) modulation, the frequency requirements of the RF local oscillators and the optical modulators are reduced to 10GHz, which means a cost-effective RoF implement. Since the mm-wave signals in the photocurrent are generated by beating in a SSB pattern, the optical mm-wave signal has great tolerance to the fiber dispersion. Moreover, one optical mm-wave carrier carries two16-QAM 10Gb/s data streams, our link scheme has a higher bandwidth efficiency. The simulation results show that both the constellation diagrams and the eye diagrams of the two different QAM streams are well accepted even after 60 km fiber transmission.

An all-optical frequency-upconversion based on fractional talbot effect is experimentally reported. The 2.5-Gb/s baseband signal carried on 10GHz pulse trains is upconverted to 40GHz millimeter wave after 18.49km transmission via repetition frequency multiplication of pulse trains. The phase noise of the 40GHz is as well as -92dBc/Hz at 10kHz frequency detuning. This scheme can operate in 60GHz band by employing the appropriate fiber length based on fractional talbot effect.

Simulations confirm stable MIMO transport of two channels over a two-mode fiber. Successful reception is achieved over 80km two-mode fiber at a bit error rate of 10^-6 - enabled by a new signal recovery algorithm we proposed.

We design a high-performance LP₁₁ spatial mode combiner using elliptical-core two-mode fibers. Two input LP₀₁ modes are selectively coupled into two LP₁₁ modes with a coupling-efficiency of 65~96% within a broad wavelength-range of 1505-1600 nm.

This paper is dealing with the non-linear distortion of different optical modulators including directly modulated laser diode (LD), Mach-Zehnder modulator (MZM) and reflective semi-conductor optical amplifier (RSOA), which are candidates of optical device used to make colorless ONUs. To analyze the performance of different optical modulators a unified mathematic model is developed in which the optical OFDM signal output from an optical modulator is expressed as a power series including 1^-st order and higher order terms. Based on this statistical model, the performance of the modulators are computed and compared. The effect of third order distortion in modulating signal on error vector magnitude (EVM) is particularly evaluated for optimizing the fiber transmission link.

We show the application of closed-form expressions for nonlinear transmission performance of coherent optical OFDM systems with frequency guard band. The dependences of their performances on system parameters are investigated and new findings on the influence of dispersion compensation configuration and guard band are observed. The advantage of using closed-form expressions is that the performance for various system configurations can be identified without resorting to sophisticated numerical simulations.

We detail a methodology to avoid pitfalls while investigating the upgrade of legacy 10G transmission systems with 40G DP-BPSK or 100G DP-QPSK channels using numerical simulation. Techniques for efficient and accurate estimation of intra- and inter-channel nonlinear effects are discussed.

We propose a general method to monitor the impairments in high speed multilevel signal modulation format generation induced by improper setting and time-drifting of modulator bias offset based on signal constellation diagram. Using asynchronous linear optical sampling technique, we can obtain both the amplitude and phase information of the signal under test with a high time resolution and data speed transparency. We successfully recovered the constellation diagrams of 10Gbaud quadrature phase shift keying (QPSK) after a series proposed signal processing algorithms. Several common types of constellation distortion were observed with the manual tuning of the modulator bias. It proved the effectiveness of the proposed method.

We proposed an ultra-wide range chromatic dispersion (CD) measurement method using coherent detection and digital signal processing. We measured the average phase at frequency ± f as a function of frequency f, and estimated the total accumulated CD with polynomial fitting algorithm. The method is compatible with modern coherent optical networks and capable of measuring CD of at least ± 16000 ps/nm with an accuracy of better than ± 50 ps/nm.

The influence of higher-order harmonics produced in modulator on flat and stable optical comb generation based on recirculating frequency shifter (RFS) for all-optical OFDM is analyzed and demonstrated in this paper. We also theoretically analyze the condition for flatness of the optical frequency comb. The resulting theoretical analysis is confirmed by a 16 comb lines and 12.5 GHz spacing RFS generation system. The results demonstrate that flat and stable optical comb generation based on RFS can be a useful solution for multi-wavelength source in all-optical OFDM.

We propose a simple and novel solution for 40G and higher rate optical transport. It elaborately employs state of polarization without relying on complicated receiver structures, such as Stokes receivers, polarization controllers. By altering both polarizations and phase of lightwave, it can increase the spectral efficiency. As a constant power modulation format and an alternative polarization modulation format, D-mPSK-PolSK is highly tolerant to fiber nonlinearity.

Pilot pattern and pilot density are often used for channel estimation in optical/electronic orthogonal frequency division multiplexing (OFDM) systems. To enhance the performance of the channel estimation of OFDM systems, the transmission of the OFDM signals is experimentally investigated via different pilot tone arrangements for effective channel estimation. Three types of pilot patterns (comb-type, block-type and incline-type) are used to evaluate the output OFDM signal in terms of error vector magnitude (EVM), based on the most commonly adopted low complexity Least Square (LS) channel estimation algorithm. It has been shown that, the pilot insertion will definitely improve the quality of the transmitted OFDM signals up to 6 dB in EVM. The best channel estimation is obtained by the block-type pilot pattern, which gives nearly 1dB gain in EVM compared with the other two patterns, implying the measured channel of the electronic cable is relatively quasi-static.

In order to further improve the laser phase noise tolerance of coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems, an iterative phase noise suppression algorithm is proposed in this paper, which is powerful in mitigating the laser phase noise induced intercarrier interference (ICI) even when laser linewidth achieves 2 MHz. Compared with the existing ICI suppression method, the performance gain brought by the proposal is significant when the laser linewidth is larger than 1.5 MHz. The BER floor which can not be avoided by using the existing phase noise suppression methods can be reduced effectively by employing the new iterative algorithm.

We compare the cost-efficiency of optical networks based on mixed datarates (10, 40, 100Gb/s) and datarateelastic technologies. A European backbone network is examined under various traffic assumptions (volume of transported data per demand and total number of demands) to better understand the impact of traffic characteristics on cost-efficiency. Network dimensioning is performed for static and restorable networks (resilient to one-link failure). In this paper we will investigate the trade-offs between price of interfaces, reach and reconfigurability, showing that elastic solutions can be more cost-efficient than mixed-rate solutions because of the better compatibility between different datarates, increased reach of channels and simplified wavelength allocation.

Power reduction and throughput enhancement are critical issues in core/metro networks in creating future networks. Exploiting optical technologies is the way to achieve both goals. Focusing on traffic grooming, important optical technologies that enhance the agility and elasticity of optical paths are discussed.

This paper will at first explain the requirement of high speed optical transport network on forward error correction (FEC) codes in terms of code length, code rate, coding gain, burst error correction capability, error floor, latency, coding/decoding complexity. Then, a few code schemes used in current optical transport systems such as Reed-Solomon codes recommended by ITU-T G.709 and enhanced FECs listed in ITU-T, G.975.1 are introduced. Advanced codes recently developed by vendors used for 100Gbps systems and their performances are summarized. Features and special requirements on soft decoding FEC (SDFEC) especially inter-working between SDFEC and equalizer, with and without deferential coding etc. are analyzed. Some perspectives of future FEC for optical transport are also given.

In this paper we review our previously-proposed direct-detection optical OFDM superchannel and the corresponding optical-multiband receiving. With this technique we have successfully demonstrated the transmissions of 720- and 1200-km SSMF, respectively, at 214- and 117-Gb/s data rates.

Scaling of computing systems require ultra-efficient interconnects with large bandwidth density. Silicon photonics offers a disruptive solution with advantages in reach, energy efficiency and bandwidth density. We review our progress in developing building blocks for ultra-efficient WDM silicon photonic links. Employing microsolder based hybrid integration with low parasitics and high density, we optimize photonic devices on SOI platforms and VLSI circuits on more advanced bulk CMOS technology nodes independently. Progressively, we successfully demonstrated single channel hybrid silicon photonic transceivers at 5 Gbps and 10 Gbps, and 80 Gbps arrayed WDM silicon photonic transceiver using reverse biased depletion ring modulators and Ge waveguide photo detectors. Record-high energy efficiency of less than 100fJ/bit and 385 fJ/bit were achieved for the hybrid integrated transmitter and receiver, respectively. Waveguide grating based optical proximity couplers were developed with low loss and large optical bandwidth to enable multi-layer intra/inter-chip optical interconnects. Thermal engineering of WDM devices by selective substrate removal, together with WDM link using synthetic wavelength comb, we significantly improved the device tuning efficiency and reduced the tuning range. Using these innovative techniques, two orders of magnitude tuning power reduction was achieved. And tuning cost of only a few 10s of fJ/bit is expected for high data rate WDM silicon photonic links.

All-optical OFDM data transmission opens up a new realm of advanced optical transmission at extreme data rates, as subcarriers are multiplexed and demultiplexed by all optical discrete Fourier transforms (DFT). This paper reviews the principles of all optical OFDM transmission and its system application techniques, providing the generic ideas and the practical implementation issues to achieve 100Gbps or higher data rates with a spectral efficiency of 1 bps/Hz or better. This paper also include discussions on all-optical OFDM implementation variants such as an AWG-based OFDM multiplexer and demultiplexer, a receiver design without optical sampling, a transmitter design with frequency-locked cw lasers, an OFDM cyclic prefix designs, and a chromatic dispersion mitigation technique.

An experimental study of the reach of coherent 40 Gb/s PDM RZ QPSK transmission on two different testbeds at several spectral efficiencies is presented. Performance using differential phase detection (DQPSK), differential coding (DCQPSK) and absolute phase detection (QPSK) in digital processing is investigated. The system reach at spectral efficiency of ≥1.2 bits/s/Hz is investigated on a transmission path made up of large effective area fiber with no optical dispersion compensation. Transpacific transmission distance at 3.2 bits/s/Hz and record SE-distance product at 2.4 bits/s/Hz are demonstrated.

We demonstrate an optical transmission system based on a 6-level PSK modulation format and differential detection with a partial symbol delay. The 6-level PSK signal is simply generated by using a chirp-free Mach-Zehnder modulator followed by a phase modulator. In order to convert the phase information of the 6-level PSK signal into the intensity, we utilize a pair of two Mach-Zehnder delay-line interferometers with having a differential delay less than the symbol duration of the signal unlike a conventional differential detection scheme. We evaluate the performances of the differential 6-level PSK signal and compare them with that of a conventional DQPSK signal. In addition, the transmission performance of the 21.4-Gb/s 6-level PSK signal is experimentally verified in a 240-km long dispersionmanaged fiber link. Furthermore, additional simulation results show that the tolerance to optical filtering and chromatic dispersion of the 107-Gb/s differential 6-level PSK signal is improved significantly by adopting the partial demodulation scheme.

We present coherent phase modulation detection for laser phase noise measurement via a self-heterodyne technique. Measurements have been performed for DFB and SGDBR lasers to demonstrate the technique. The results show that DFB laser phase noise is well described by the random-walk phase fluctuation while SGDBR has additional frequency fluctuation due to 1/f noise below 100 MHz that significantly broadens the linewidth.

The introduction of OFDM into PON networks is to leverage the merits of OFDM to provide the flexibility and reduce the cost. In this paper, we present our latest works on OFDM-PON. Firstly, we propose and demonstrate a novel OFDMPON upstream transmission architecture with traffic aggregation by orthogonal band multiplexing. The multiplexed 10- Gb/s OFDM signal is collectively received. We also conduct a proof-of-concept experiment to verify the architecture. Secondly, we propose and experimentally demonstrate wavelet packet transform based OFDM (WPT-OFDM) using real-valued transforms, which enables the cost-effective intensity modulation/direct detection (IM/DD). Unlike conventional FFT-based OFDM, the need for cyclic prefix is eliminated due to the time-frequency localization properties of the wavelet.

A high sensitive and low distortion amplification design was carried out in the uplink of the WiMAX Radioover- Fiber PON that was configured with a 1:8 splitter and a 30km-SMF. The EDFA gain compensates the optical loss of the optical components and SMF. The gain of the LNA of the PIN-PD is not high so that the LNA output power does not exceed -15dBm. The gain of the LNA of the DFB-LD driver is higher than the difference between the input power and 20dBm. We achieved a low Relative constellation error (RCE) of -25dB at the input modulation power of -60dBm. An estimation of the power diagram to achieve -80dBm sensitivity with 60km SMF was carried out.

We design a greedy scheduling algorithm for resource assignment in OFDMA-PON, which makes one of the best choices at every step. The proposed algorithm demonstrates high channel utilization and less Total Grant Time.

In this paper, a numerical investigation on the nonlinear distortion of OFDM (Orthogonal Frequency Division Multiplexed) signals caused by RSOA (Reflective Semiconductor Optical Amplifier) as an intensity modulator in OFDM-PON system is undertaken. Based on curve fitting approach a fourth order polynomial is, for the first time, used to present the nonlinear gain of RSOA. The expression of in-band and adjacent-band noise due to nonlinear distortion is then derived. Besides, the EVM of system versus input signal power is simulated by VPItransmissionmaker7.6, the results indicate the nonlinear effects-induced degradation of transmission performance depends highly on the third order term of nonlinear distortion power, and the optimum input signal power is provided to improve the transmission performance. Finally, it's worth mentioning that the quantified analysis method is applicable for the nonlinearity analysis of any RSOA-Based OFDM-PON system.

We create a 40Gbit/s multi-lane distribution (MLD) interface converter for STM-256 to STL-256.4 and OTU3 to OTL3.4. We successfully demonstrate a cost-effective optical transceiver for STM-256/OC-768/40G-POS by using our 40Gbit/s MLD interface converter prototype.

A new symbol timing synchronization scheme based on a tailored training sequence is proposed and implemented in direct modulation and direct detection optical OFDM PON (DM-DD OFDM PON) systems. This tailored training sequence is added in front of OFDM data symbols. By using the received signal correlation operation, receiver calculates the peak value of metrics to achieve accurate symbol timing synchronization. The performance of this new timing synchronization scheme is presented by simulation and experiment. The results show that the proposed scheme has high synchronization accuracy and is suit for DM-DD OFDM PON system.

Compared to other digital equalizers, MLSE (maximum likelihood sequence estimator) equalizer seem to be the most promising candidate solution to mitigate impairments caused by CD, PMD and fiber's nonlinearity. A novel MLSE equalizer technology combined with FFE based on nonlinear Volterra theory is investigated, which shows superior performance for joint compensation of all distortion effects in uncompensated 40Gbit/s Pol-Mux RZ-DQPSK optical transmission system. The receiver can achieve a long haul transmission with 280 km without any optical dispersion compensation.

In this paper, a novel dual-polarization differential quadrature phase shift keying (DQPSK) system is proposed, which does not need polarization de-multiplexing like the conventional polarization division multiplexing QPSK, but bases on just one receiver. Its performance including the tolerance to chromatic dispersion (CD) and to polarization mode dispersion (PMD) is analyzed. The result shows that the tolerance to CD and PMD of the novel system is nearly same to that of DQPSK system with the same bit rate, but it can bring down the electrical signals rate at the transmitter.

We demonstrate transmission of 1.0-Tb/s unique-word DFT-spread OFDM signal over 8000-km SSMF with 80-km span length and EDFA-only amplification, representing a record spectral efficiency and reach product compatible with most of the deployed links.

We report the first terabit/s superchannel transmission over a submarine distance >10,000 km. Four 1.15-Tb/s superchannels, each consisting of 23 optical subcarriers at 12.5-GHz spacing are modulated with DP-QPSK at 12.5 Gbaud. The WDM signal is transmitted over 168×60.6-km spans of hybrid large-core/ultra low-loss fibers with inline amplification by low noise C-band EDFAs. The system achieved a Q-factor margin of 2 dB assuming the use of HDFEC, and a spectral efficiency of 3.6 b/s/Hz is achieved.

An adaptive algorithm of fine synchronization for coherent optical orthogonal frequency division multiplexing (CO-OFDM) transmission system is proposed. The whole synchronization is separated into two steps. In the first step, we use an auto-correlation-style algorithm to achieve the coarse symbol synchronization. In the second step, the proposed algorithm is used to achieve the fine synchronization. The merit of the proposed algorithm is that it can realize fine synchronization under different environments without adjusting the detect-threshold of timing metric in a dynamically reconfiguration network. The numerical experiment result demonstrates that the proposed algorithm achieves fine synchronization under different signal noise ratio (SNR) conditions after 6 fiber-spans transmission.

This Letter proposes a low-cost Optical Frequency Multiplication (OFM) scheme based on dual drive Mach-Zehnder Modulator (DD-MZM) to generate 40-GHz millimeter-Wave (mmW) signals and 32Gbps 64QAM-OFDM signal at the center frequency of 35GHz occupying 5.6GHz bandwidth applied to Radio-over-Fiber (RoF) system. The optimal driving power of Intensity Modulator (IM) is also discovered to achieve the smallest EVM (Error Vector Magnitude) for the RoF system.

This paper is concerned with the effect of the nonlinearity of an MZM (Mach-Zehnder modulator) on optical OFDM signal distortion. The optical OFDM signal output from the MZM is expressed as a Taylor series including third-order and fifth-order nonlinear distortion terms, by which we can easily establish a mathematical model of the optical OFDM signals in different formats and rates. According to the model, we can get the EVM at the optimized point. Moreover, the proposed theoretical model is proved in good agreement with experiment results of the RoF (Radio over Fiber) system.

The purpose of this paper is to numerically study performance improvement of single-channel secure chaotic optical communications utilizing symmetrical dispersion compensation technique. The decrypted 1.25-Gbits/s non-return-tozero (NRZ) sequence at the receiver side becomes rather distorting after the transmission of 200-km dispersion shifted fiber. However, the quality of decrypted sequence is significantly improved by allocating dispersion compensation fiber. The results show that the Q-factors of the latter dispersion compensation period are smaller than that of the former ones. This is mainly due to the self-phase modulation (SPM) induced by the nonlinear coefficient of fiber. The results also indicate that the Q-factors increase in different degrees for three sequences of different bit rates.

We have experimentally demonstrated a 40Gb/s all-optical binary-coded-decimal (BCD) decoder for the first time, utilizing delay interferometers (DIs) and cascading semiconductor optical amplifiers (SOAs) without any assisting light. Extinction ratios (ERs) of the intermediate results after the first SOA are all over 11dB which ensures the capability to cascade to the second one. The final results are in the form of return-to-zero (RZ) format with correct and clear temporal waveforms. The proposed scheme could be extended to 1-of-16 decoder, logic minterms and read only memory (ROM).

PM-DQP-ASK is a promising technique to achieve bit rates greater than 100Gbit/s and high spectral efficiency, both essential for future optical networks.We demonstrated 20 Gbaud PM-DQP-ASK and its successful transmission in a 100 GHz-spaced 10 Gbit/s NRZ-OOK WDM systems over a 768-km transmission link along with the studies of WDM nonlinear crosstalk.

For the first time, we propose a novel BER estimation algorithm for 8PSK signal, the idea of which is also applicable to other multi-dimensional and multi-level modulation formats. And a 2 × 4 orthogonal optical label swapping based on 120Gb/s 8PSK payload and 78Mb/s ASK label by using optical switching devices is demonstrated. Through numerical simulations under different circumstances, we get some orthogonal label switching network's characteristics by analyzing the receiver BER utilizing the new BER algorithm, such as that different combination of label will have a different impact on the transmission performance of the packets. In addition, by changing the receiver optical power, transmitter optical power and optical power launched into the fiber, we get the system's receiver sensitivity, the optimum transmitter power and optimum optical power injected into the fiber, which will be a reference for the actual systems' design.

The high-speed parallel optical transmitter module based on VCSEL/PD array, high-speed specialized integrated circuit, fiber array micro-optical components presents magnificent application and development potential. The coupling alignment between VCSEL/PD array and waveguide array has been reported using silicon optical bench (SiOB) [1-3]. In this paper, A passive coupling method based on SiOB and the packaging of the VCSEL/PD arrays are introduced; the coupling efficiency is about 80% with a misalignment tolerance of +/-15μm, optical cross talk is about -70dB. A silicon optical bench is fabricated as a platform for integrated photonic components. The thermal performance and electrical performance of optical sub-package is analyzed and optimized. A High density SOP Optical Transceiver is designed based on this coupling method. Signal integrity analysis and optimization of the high-density differential signal pairs on PCB is conducted and S parameters are extracted to optimize impedance and minimize the effects of discontinuity in the electrical channels. In addition, to suppress simultaneous switching noise (SSN) and optimize the target impedance, a novel embedded capacitor filter is used instead of the conventional power supply filter, the film capacitor measures 14μm in thickness, has a dielectric constant of 16 and a capacitance density of 1nF/cm². The transceiver loop back diagram is shown; the bit error rate of the optical transceiver is tested loop back with a 2³¹-1 PRBS pattern and found to be 10^-12s^-1 at 10Gbps while dissipating 90mW/channel.

An efficient bit-to-symbol mapping method for star 16-quadrature amplitude modulation (16-QAM) is proposed in this paper, which is similar to Gray coding for square 16-QAM. With the consideration of optimal ring ratio of constellation, our simulation results show that a linewidth of 3MHz per laser can be tolerated for star 16-QAM optical coherent systems with SNR penalty of 1dB at BER of 10^-3, which is much better than that of square 16-QAM. Further optimization possibility with variable number of points on each of the rings for star 16-QAM constellation is also discussed.

Pilot patterns and interpolation algorithms are of great importance to the performance of pilot-assisted channel estimation in optical OFDM systems. Traditionally a number of pilot tones are periodically inserted into the OFDM symbols for the estimation of the channel state, for instance, the least-square (LS) linear interpolation was a traditional approach to estimate the phase rotation of the subcarriers. In this paper, we present a novel interpolation algorithm with better performance than linear interpolation method while maintain similar complexity. Simulations in a 10 Gb/s direct detection optical OFDM (DDO-OFDM) system show that the algorithm greatly improves the constellation convergence.

Based on phase manipulation of optical frequency combs and square-law detection of the waveforms, low phase-noise frequency with its tunable repetition frequency ranging from 10GHz to 120GHz is generated using a dispersive medium fed by coherent optical frequency combs with frequency interval controlled by pulse pattern generator. Both temporal waveforms and phase noise are evaluated. The phase noise of generated 40GHz tone is -96.9dBc/Hz at 10 kHz offset.

A scheme of optical 16-QAM signal generation based on XPM in nest semiconductor optical amplifier based Mach-Zehnder interferometer (SOA-MZI) is proposed. In this proposal, 10Gbit/s QPSK and 16-QAM signal can be generated. Simulations and theoretical analysis have been conducted to validate the feasibility of the proposal by VPItransmissionMaker 8.5. A power penalty below 1.75dB is obtained after the transmission over 160km along single mode fiber with a receiver sensitivity of -28.5dBm.

White light-emitting diodes (LEDs) are becoming widely used in both illumination and communication applications. In this paper, a visible light communication system is described, which employs blind equalization schemes at the receiver. The blind equalization schemes can both improve the data transmission bandwidth significantly and compensate the signal distortion dynamically. Off-line analysis shows the eye-diagram is observably improved at 10 Mb/s operations using 1 MHz bandwidth white-light LED.

We propose and demonstrate a simple and robust short pulse source based on chirp compression scheme and Mamyshev 2R regenerator. Pedestal-free optical pulse with repetition rate of 25 GHz, FWHM of 1.33 ps and RMS timing jitter of 112.81fs (100-Hz~10-MHz) is generated experimentally. Moreover, it is successfully applied to a 200-Gbit/s OTDM system by multiplexing in time domain.

A novel scheme for automatic demultiplexing used the partial low frequency radio frequency (RF) power as control signals for polarization division multiplexed (PDM) system is proposed firstly. The spectrum of detected signals, which is sensitive to the angle between polarization controller (PC) and the polarization beam splitter (PBS), are thoroughly analyzed. The effectiveness of this demultiplexing method is experimentally demonstrated.

In this paper, we conduct a simulation for WDM-PON with coherent optical OFDM using partial carrier filling (PCF) configuration. The impact of PCF patterns and PCF factor on transmission performance at 40-Gb/s over 100 km are studied and simulated. The influence of power into fiber is examined to obtain the optimal value corresponding to the expected transmission distance.

An analytical model for evaluating the performances of PMD-supported dual-channel, direct-detection optical PolSK transmission systems with a simple-structure, pre-amplified receiver is presented. The BER in each channel and an average BER of the system are evaluated based on the calculations of the noise probability density functions by using the Karhunen-Lo`eve expansion and moment generating function. The PMD effects in the fiber link are taken into account. Based on the proposed model, the calculated results for evaluating performances of the PolSK system are presented.

In this paper, we propose a novel bandwidth-flexible reconfigurable optical add/drop multiplexer (ROADM) architecture based on coherent optical-orthogonal frequency division multiplexing (CO-OFDM) technology. The bandwidth-flexible ROADM architecture enables sub-wavelength, superwavelength, and multiple-rate data traffic accommodation in a highly spectrum-efficient manner, thereby providing a fractional bandwidth service. We simulate and compare the blocking performance of bandwidth-flexible ROADM with and without wavelength converters. It is found that wavelength converter could obviously improve the blocking performance of bandwidth-flexible ROADM with different frequency grid. Moreover, the conversion ratios are calculated for different load and channel spacing. Based on the analysis of conversion ratio, we could make an appropriate configuration of wavelength converters in bandwidth-flexible ROADM.

A novel scheme that employing the coherent receiver in atmospheric laser communication system was proposed in this paper. DPSK format modulation is adopted to overcome atmospheric turbulence and multipath fading. Coherent receiver is used to improve system's sensitivity. Testing bed was setup and eye diagram can be measured. Real time BER would be measured soon.

A novel and practical compressive sampling system is proposed based on optical mixing and direct detection and our system is established with a multi-wavelength source, two intensity modulators, an electric M-sequence generator, and multiple photodetectors. In experiment, a compressive sampling system of two channels is set up, which is firstly reported, and the predefined signal including two narrow-band components is recovered successfully for 2.55GHz bandwidth.

The optical transmission system is being upgraded from 10G to 40G even 100G due to the increasing demands of wide-bandwidth network. We numerically investigate the nonlinear tolerance of 112 Gb/s polarization-multiplexed return-to-zero differential quadrature phase-shift keying signal with different types of neighboring channels on a 50-GHz grid over 1,000 km field fiber. Our transmission result proves showing the feasibility of 100G overlaying existing 10G/40G commercial systems despite the presence of strong cross-phase modulation.

The performance of DPSK and DQPSK with NRZ, 33% RZ and CSRZ formats are numerically compared and investigated for 160 Gbit/s single channel transmission system. The impairments caused by chromatic dispersion (CD), higher-order chromatic dispersion, nonlinearity and accumulated noise are considered. The primary limitation for those modulation formats in 160 Gbit/s transmission system is investigated.

The paper proposed a novel hybrid modulation format -16-level differential phase shift keying with binary amplitude shift keying(16DPSK-ASK), which carries 5 bits per symbol. With analyzing the characteristics of optical 16-level differential phase shift keying (16DPSK), the study analyzed 16DPSK-ASK modem methods theoretically and presented the methods in their achieving processes specifically. Based on RZ-16DPSK-ASK and CSRZ-16DPSK-ASK modulation methods, spectra and their eye diagrams following demodulator of Matlab simulation were obtained. The optimal back to back extinction ratio was derived, so that the equivalent eye opening was obtained for the amplitude tributary and phase tributary. The results showed that the 16DPSK-ASK hybrid modulation methods, as a possible new modulation format, not only have much narrower spectra with higher spectrum efficiency but also simplify the transmitter and receiver comparing with the same level modulation format. The satisfactory performance of the eye diagrams obtained after demodulation suggested that it was one of the dominant candidate modulation formats high-speed optical transmission system.

A novel photonic scheme of instantaneous frequency measurement (IFM) using analog modulation links with interferometric detection assisted by a polarizer is proposed and demonstrated experimentally. This scheme is simple, cost-effective as it only requires the basic modulation-demodulation elements in typical analog optical links. The measurement errors as shown in experimental results can be kept in 0.1GHz over a frequency range of 0.1GHz-6.5GHz.

In this paper, we propose an effective possibility density functions method of channel estimation with Viterbi algorithm based on transitions. We also investigate the performance of the electronic dispersion compensation schemes via this new channel estimation method. The schemes Simulation results show that it exhibits the similar performance with the sophisticated MLSE scheme.

We discuss the influence of the seams between the liquid crystal pixels on the signals that transmits through the LCoSbased switching node in the elastic optical path network. It is found that the seams will bring repetitions of the signal in time domain. Also, the spacing and amplitudes of these repetitions are determined respectively by the spectral spacing and the shapes of the frequency slots implemented by the liquid crystal pixels. By simulating with an LCoS-based switching node model, we propose a feasible approach to reduce this influence.

In this paper, we present the simulation results on the investigation of the impacts of PMD on the PolSK optical transmission system. The model used for this study is a dual-channel, direct-detection PolSK optical transmission system with improved receiver architecture. The quality Q factor of system is used as a parameter to evaluate quantitatively PMD effects on the performances of this dual-channel PolSK system. The simulation results show that the PMD severely impairs the transmission performances of the PoLSK system and resultantly limits the bit rate. The results also show that with PMD compensation, the performances of the PolSK system can be effectively improved and the bit rate increases greatly from 6 Gb/s to 22 Gb/s.

We present analysis of different modulation formats using actual Polarization Mode Dispersion (PMD) data of deployed fiber links in the metro area in Kuala Lumpur, Malaysia. Simulations have been conducted for comparing the performance of Non-Return-to-Zero (NRZ), Return-to-Zero (RZ), Carrier-Suppressed Return-to-Zero (CSRZ), Phase Shaped Binary Transmission (PSBT) and Differential Quadrature Phase Shift Keying (DQPSK) modulation formats for possible future upgrade to 40Gbps from an existing 10Gbps DWDM system. The performance in terms of BER is presented to illustrate the limitations attributed to PMD based on current existing network configurations.

We propose a novel approach to compensate the fiber chromatic dispersion (CD) and to adjust the phase/amplitude using two pilot tones in fiber optical OFDM transmission. In the conventional channel estimation methods, one or more symbols have to be applied as the pilot tones. The new approach makes full use of the fiber CD properties while using less pilot tones. The simulations show a significant improvement (~ 2 dB) of the optical OFDM signal in terms of the bit error rate (BER) penalty, compared with the conventional least-square (LS) linear interpolation and one-reference-symbol methods.

Two different semi-analytical methods for error probability estimation in PDM-QPSK optical communication systems are investigated. We consider the accuracy of a stochastic semi-analytical method based on Gaussian noise statistics and a deterministic semi-analytical method where the noise probability density function is estimated analytically against Monte-Carlo simulation. Linear coherent PDM-QPSK systems with distortions induced by filtering only, and nonlinear coherent PDM-QPSK systems with or without inline dispersion compensation are studied. Our results suggest that the stochastic semi-analytical method based on Gaussian noise statistics works very well for practical fiber-optic communication systems.

This paper introduces in detail a novel 40-GHz radio over fiber (RoF) system based on optical frequency multiplication with up to 1.4Gbps 16QAM-OFDM wireless signal employing a Mach-Zehnder modulator with no optical filtering. And also what is discovered as expected during the experiment --- the optimal driving power of the intensity modulator (IM) to relieve high peak-to-average power ratio (PAPR) of OFDM signal on intensity modulator with an acceptable SNR.

We show that for coherent 112 Gbps PDM-QPSK systems employing inline dispersion management, and for a wide range of birefringence parameters, spinning reduces the benefit of local birefringence in the mitigation of nonlinear impairments.

We propose a novel synchronization scheme using a periodic light pulse for free-space quantum key distribution (QKD) system. For our 10MHz system, the repetition rate of timing pulse in the novel synchronization scheme can be reduced to 100 KHz or even lower. It allows employing a KHz repetition rate ultrashort pulse laser as timing synchronization source to implement high precision time synchronization. In this paper, short term time drift induced by atmospheric turbulence is analyzed, and how the time deviation impacts on the final secure key generation rate in our QKD system is calculated. In addition, we carried out the QKD experiments over the distance of 1.38 km. The results of the experiments indicate that our scheme is feasible.