This PDF file contains the front matter associated with SPIE Proceedings Volume 11891, including the Title Page, Copyright information, and Table of Contents.

Frequency-chirped microwave waveforms have high pulse compression ratio and are widely used as radar waveforms to increase the detection range and range resolution. In radar networks, the frequency-chirped microwave waveforms generated in center office (CO) need to be transmitted to remote base stations. During fiber transmission, the dispersion of long-distance fiber may cause power fading to the radar waveforms which restricts the signal frequency, signal bandwidth and transmission distance. In this paper, we review our recent works about photonic generation and antidispersion transmission of frequency chirped microwave waveforms. First, based on polarization multiplexing Fourier mode-locked optoelectronic oscillator, frequency and bandwidth doubling chirped microwave signals are generated. By adding a laser, the system can also generate dual-chirp signals. Second, by combining the generation and transmission of dual-chirp microwave waveforms, we proposed a photonic scheme for the generation and transmission of dual-chirp microwave signals based on shifting the power fading frequency response to compensate the fiber dispersion. In order to further improve the bandwidth of dual-chirp waveforms and the anti-dispersion transmission capability, we used optical frequency doubling and carrier frequency shifting technology to achieve quadruple-bandwidth dual-chirp signal generation and transmission with the elimination of power fading. Moreover, an equivalent splitting parabolic phase modulation scheme was proposed to generate background-free dual-chirp microwave waveforms, which is independent of the direct current bias points of the modulator and the polarization states of the system. The system can eliminate the power fading induced by fiber dispersion in principle, which has good application prospects in radar networks.

Nowadays, the coherent optical communication system plays an important role in communication field because of large capability and bandwidth. A coherent optical communication, based on high-order modulation and digital signal processing technologies, consists of optical transmitters, optical fiber lines, optical amplifiers and optical receivers. In the high-speed coherent optical communication system, the phase noise from the transmitter laser and the local oscillator laser can significantly degrade the performance of the signal transmission and detection, especially for the systems using high-order modulation format, such as m-ary phase shift keying (mPSK) and m-ary quadrature amplitude modulation (m-QAM). Therefore, investigations on laser phase noise compensation algorithm based on digital signal processing technologies has become more and more significant. In this work, a multi-ring carrier phase recovery algorithm is developed for compensating the laser phase noise in optical fiber communication systems using high-order modulation formats. Degradations on the performance of communication systems due to the laser phase noise have been investigated. The system performance using the proposed algorithm and the conventional Viterbi-Viterbi algorithm were also evaluated in 9-channel and 15- channel, 32-Gbaud, Nyquist-spaced QPSK, 16-QAM, 64-QAM and 256-QAM coherent transmission systems with considering the impact of the laser phase noise. It is found that the phase noise leads to stricter constraints on the linewidths of transmitter-side and receiver-side lasers, and it can greatly degrade the achievable information rates in communication systems. Besides, compared to the conventional Viterbi-Viterbi algorithm, which is usually applied in the QPSK system, our proposed algorithm can also well mitigate the laser phase noise in 16-QAM, 64-QAM and 256-QAM optical communication systems.

Fiber-optic communication systems have advantages of low attenuation, long distance, broad bandwidth and robust to the electromagnetic interference. Nevertheless, conventional fiber-optic communication systems always work at room temperature or below 85°C, which makes it difficult to use in high-temperature environment. Communication devices including laser source and optical transceiver cannot work under high temperatures. In some special situations or industrial applications, the temperature of surrounding environment can be over 100 °C, which is far beyond the temperature limitation of general optical communication system. This limits the application of fiber-optic communication in the high-temperature environment. The method of fiber-optic communication system working at high temperatures is researched and designed. Hightemperature optical communication devices including high-temperature laser diode with drive program and hightemperature photoelectric detection circuit are developed. These devices were tested in simulated high temperature environment. The experimental results demonstrated that the fiber optic communication system is capable of working steadily over a long time in high-temperature environment to realize broadband and remote transmission of optical information. Moreover, the high-speed transmission method under high temperatures is developed, which enable realtime, long-range, high data rate bidirectional transmission. The method allows optical information to be transmitted in high-temperature environment, which can apply to industrial control and extreme environment operations, like oil and coal mining, where high-reliability, real-time performance and high-capacity are needed.

The efficient and accurate evaluation of the transmission performance of high-capacity optical communication systems has always attracted significant research attentions. The enhanced Gaussian noise (EGN) model is considered as an excellent solution to predict the system performance taking into account linear and nonlinear transmission impairments. Since the conventional form of the EGN model is complicated and intractable for a fast computation, the closed-form simplification has been regarded as a direction to significantly reduce the computational complexity. However, the accuracy of such a closed-form EGN model becomes a main concern in the application of ultra-wideband optical communication systems. In this work, we have investigated the accuracy of the closed-form EGN model for ultra-wideband optical fiber communication systems, where the performance of the system using electronic dispersion compensation, multi-channel nonlinearity compensation and full-field nonlinearity compensation has been evaluated in terms of symbol rate, number of channels and signal power. Our work will provide an insight on the application of the EGN model in next-generation ultra-wideband long-haul optical fiber communication networks.

In digital signal processing (DSP) based coherent optical communication systems, the effect of equalization enhanced phase noise (EEPN) will seriously degrade the transmission performance of high-capacity optical transmission system. In this paper, we have investigated the influence of EEPN on 9-channel 32-Gbaud dual-polarization 64-ary quadrature amplitude modulation (DP-64QAM) Nyquist-spaced superchannel optical field trial by using electronic dispersion compensation (EDC) and multi-channel digital backpropagation (MC-DBP). The deteriorations caused by EEPN on the signal-to-noise-ratio (SNR) and achievable information rates (AIRs) in high-speed optical communication systems have been studied. The system performance versus back-propagated bandwidth under different laser linewidth have also been demonstrated. The SNR penalty due to the distortion of EEPN achieves ~5.11 dB when FF-DBP is implemented, which informs that FF-DBP is more susceptible to EEPN, especially when the LO laser linewidth is larger. The system AIR versus different transmission distance under different EEPN interference using EDC-only and MC-DBP have also been evaluated, which show that there is a trade-off on the selection of lasers and back-propagated bandwidths to achieve a target AIR.

Based on a weak-resonant-cavity Fabry-Perot laser diode (WRC-FPLD) with dispersive optical feedback provided by a linearly chirped fiber Bragg grating (LCFBG), we propose a scheme for simultaneously generating multi-channel chaotic signal with time delay signature (TDS) suppression. The experimental results show that under LCFBG feedback, 45 longitudinal modes within a 30-dB amplitude variation in the WRC-FPLD can be simultaneously driven into chaotic states. With the increase of feedback strength, the effective bandwidth of the generated chaotic signal gradually increases while the TDS value firstly decreases and then increases. For feedback strength from -35 dB to -15 dB, the generated chaotic signals by WRC-FPLD under LCFBG feedback possess lower TDS compared with those under mirror feedback or ring cavity feedback. Under an optimized feedback strength of -32.88 dB, the TDS value is about 0.01, which means the TDS is almost completely suppressed.

Coherent optical fiber systems can achieve long-distance, large-capacity and high data-rate transmissions. The system performance of communication systems is generally evaluated with regard to the data capacity and the transmission reach. In this work, the performance of multi-channel (up to C-band) Nyquist-spaced coherent optical communication systems has been assessed in terms of achievable information rates, transmission distances and signal-to-noise ratios, considering different influencing factors, such as nonlinearity compensation, signal input power and modulation format. Numerical simulations and enhanced Gaussian noise (EGN) model have been carried out for different modulation formats including quadrature phase shift keying (QPSK), 16-ary quadrature amplitude modulation (16-QAM), 64-QAM and 256-QAM. It is found that in C-band (151-channel) Nyquist-spaced systems, the achievable information rates at the transmission distance of 6000 km are 19.3 Tbit/s for dual-polarization QPSK (DP-QPSK), 30.9 Tbit/s for DP-16QAM, 32.0 Tbit/s for DP64QAM and 32.2 Tbit/s for DP-256QAM, respectively, when electronic dispersion compensation is applied only. Such achievable information rates can be increased up to 38.3 Tbit/s for DP-16QAM, 47.2 Tbit/s for DP-64QAM and 47.8 Tbit/s for DP-256QAM, respectively, when the nonlinearity compensation is employed.

A pre-distortion linearization of frequency modulation based on thermal tuning by iterative learning is proposed. The update algorithm is related both to the residual frequency error and its first-order differential. A narrow linewidth laser with a repetition rate of 100 Hz, 500 Hz, 1 kHz, and 2.5 kHz is experimentally demonstrated. When a least-squares linear fitting is applied to the averaged laser frequency sweep, the linear regression coefficient 1 − r² is calculated less than 10⁻⁷. The proposed method provides clues for the realization of the linear frequency modulation continuous wave source and has a possibility to achieve given arbitrary frequency modulation waveforms.

There is a big difference between the spot sizes of diode lasers and those of fibers or Si based waveguide, which lead to a high cost related to the assembling and packaging of lasers. To reduce the cost of optical transmitter module, it is promising to integrate monolithically a spot size converter (SSC) which expands spot size with LDs. Up to now, a number of different types of SSC have been proposed. Among them, laterally tapered SSC fabricated in the InP cladding layer of a LD needs only a simple fabrication process, helping to lower the device cost. However, it is difficult to obtained a narrow waveguide tip through conventional photolithography, which is key for high quality SSC. In this paper, we report the fabrication of a laterally tapered InP SSC in a reverse mesa shape. With an optimized wet etching condition, a reverse ridge waveguide for which the top width is significantly larger than the bottom width can be obtained. With this process, a SSC having a waveguide tip as narrow as 200 nm can be obtained with a high yield through conventional photolithography. A 1.3 μm InGaAlAs/InP laser integrated with the laterally tapered SSC has been fabricated. The threshold current of the 1000 μm long device is 25 mA and 44 mW single facet optical power can be obtained at 300 mA current. The lateral and vertical divergence angles are as low as 11° and 13°, respectively.

With the development of laser technology, high power diode lasers have found the increasing various applications in many fields, including industry, advanced manufacturing, aerospace, Lidar and medical systems etc.. The near field non-linearity (Smile) and lasing uniformity of emitters for high power diode laser arrays are critical to high reliable optically coupled modules and laser heads in a cladding system. In order to obtain the lower smile and higher lasing uniformity, two CTEmatched substrates (Copper Tungsten-CuW) are employed to bond a single GaAs-based diode laser array with the cavity length of 2mm on a Micro Channel Cooler (MCC) using Gold-Tin hard solder. This double-CuW MCC-packaged structure is called DMCC which enables a diode laser array bonded on a CuW/MCC/CuW structure with all AuSn solder. Structural optimization has been carried out to reduce the thermal stress and smile for this package. Simulation results indicate that the smile and thermal stress is lowered 0.24μm and 16MPa, respectively. According to the simulation results, single bar DMCC-packaged diode lasers with lower Smile value are fabricated and characterized. The experimental results show that the ratio of Smile (average smile ~0.87μm) ⪅1μm is ~71% and higher ~19% than that of conventional structure (average smile ~1.2μm). Importantly, the quantity ratio of lasing emitters (≥46 emitters) in a diode laser array is significantly raised from ~62% to 85% after the optimization of CuW submount.

In this paper, the investigation of gain-switching characteristics of an InAs/InP Quantum dot laser is performed for direct and cascade relaxation models, theoretically. The model is based on single mode rate equations, which are solved by the Runge-Kutta method. Moreover, the effect of external optical beam irradiation to the excited state are investigated for both relaxation models. Our results showed that for the first time, under the optical Gaussian pulse beam it is possible to generate short pulses with a width of around 30 ps with a high peak power for the direct and cascade relaxation models. It was also found that in the absence of external optical beam irradiation, width and peak power of output pulses for cascade relaxation model are slightly smaller than that of direct relaxation model whereas in the presence of optical beam, they are approximately the same for both models. Obtained results have great importance for the fields where short optical pulse is an important demand such as long-distance optical transmission and medical biotechnology.

Due to the maturity of VCSEL supply chain promoted by the VCSEL applications in smart phones, and the increasing peak power of multi-junction VCSEL chip，VCSELs are considered to have great advantages and potential as the transmitter light sources of automotive low-cost LIDAR devices. Here we introduce a kind of VCSEL line-beam module with unique optical shaping design for LiDAR applications. The module has a uniform line beam with a peak power larger than 200W, a pulse width of 4ns, a divergence angle of 0.12° @ 1/e2, and the vertical axis intensity uniformity is better than 80%. The experimental data showed that over a wide temperature range from - 40 °C to 110 °C the power variation of the line beam module is less than 20%, the variation of horizontal divergence angle is less than 5%, and the temperature drift coefficient is 0.066nm/°C, which greatly reduces the performance requirements of the receiver detector for the Lidar system. In addition, we introduce a prototype of new line-beam modules with peak power higer than 1000W we are developing, which can meet further requirement of long-distance LiDAR system.

A self-calibrated method is proposed for electrical spectrum measurement of optical frequency comb (OFC) based on segmental electro-optic up-conversion. In the method, every N comb teeth of OFC are divided into one segment in the frequency domain, and M segments are investigated with the measuring frequency range of M×N×fr (fr is the repetition frequency of the OFC). Through symmetric frequency modulation, intra-segment measurement and seamless stitching between different segments are performed. Finally, only a low-frequency microwave source is required to achieve the electrical spectrum measurement of OFC within ultra-wideband frequency range, and the measuring frequency range can be 2M-fold expanded with respect to the modulation frequency rang. Meanwhile, the frequency responses of MachZehnder modulator and photodetector are fully cancelled out, realizing the self-calibrated electrical spectrum measurement of OFC within ultra-wideband frequency range.

Optoelectronic reservoir computing (RC) is a supervised training algorithm implanted in an optoelectronic time-delay system, which possesses simple structure and can be utilized to realize pattern recognition. In this work, based on double reservoir layers composed of two Mach-Zehnder modulators (MZMs), a novel optoelectronic RC system is proposed and the system performances for processing handwritten numeral recognition (HNR) are analyzed. For such a system, a masked handwritten numeral information is injected into the first reservoir layer, the different value between two adjacent node states of the first reservoir layer is sent to the second reservoir layer, and the virtual node states of the second reservoir layer are extracted for training and testing. The simulated results show that, by optimizing the system parameters, a word error rate (WER) of 0.11 for processing HNR can be achieved. By comparing with an optoelectronic RC with a single reservoir layer, the optoelectronic RC with two reservoir layers possesses better performances for processing HNR.

In this paper, we propose and numerically demonstrate a security-enhanced high-speed chaotic communication system by introducing phase modulation and phase-to-intensity conversion. The driving laser (DL) with delayed optical feedback can be used to generate the chaotic driving signal, which is simultaneously injected into two response lasers (RLs) through a phase modulator (PM) and a dispersion component (De). The simulated results show that, due to the phase modulation and phase-tointensity conversion, TDS of injected chaos signal from DL can be effectively suppressed and its bandwidth can be increased to 39.6 GHz under suitable parameter conditions. Simultaneously injecting the chaos signal into two identical RLs, high-quality chaos signals with weakened TDS and enhanced bandwidth between two RLs can be achieved even under certain parameter mismatches, but the synchronization quality between DL and any one of RLs is extremely bad. Based on the system synchronization, secure transmission of 20 Gbit/s messages can be realized and the transmission distance can be over 200km.

In this paper, we propose and numerically investigate a novel method to generate optical frequency comb (OFC) based on mutual injection in a twin-stripe semiconductor laser (a cell array integrating two lasers on one chip in parallel). Because of the existence of optical confinement factors and the small waveguide spacing, considerable lateral coupling or mutual injection occurs between the two paralleling neighbors. The twin-stripe semiconductor laser will be driven into complex nonlinear dynamic states and can be employed to generate OFCs. The proposed mutual-injection-induced OFC generation method does not need any external microwave sources or modulators. Moreover, the compact OFC generator is free of any auxiliary optical passive devices required in the typical master-slave injection configuration. The numerical results show that the mutual-injection-induced OFC can be flexibly adjusted by changing the bias currents and the mutual injection parameters.

Three-dimensional (3D) display is a very attractive research direction, and have potential in many areas. The cutting-edge autostereoscopic display technology allows glasses-free experience, but still be limited in the lab because of the small eye space and high cross-talk. The only commercially available technology is still polarization-interlaced stereoscopic display. The disadvantages are the bulk-cost of the polarization module, low-light efficiency, and the high crosstalk. Besides, the color gamut in two-dimensional (2D) display is very important to display systems, which represents the color rending ability, and at present limited by three primaries. Herein, we demonstrate a six-primary-laser projection system compatible with 3D and 2D display, achieve great 3D viewing experience with crosstalk lower than 1% by time-multiplexed stereoscopic display technology and spectral coating glasses. In addition, we study the volume color gamut of this system in 2D working mode. The color gamut is greatly increase to an amazing 178.4% NTSC, owing to the application of multiprimary color and narrow spectral line-width laser source. This system is also provide the possibility for us to study the color gamut involving binocular fusion in 3D working mode in future.

Based on a master-slave frame, we propose and numerically simulate a scheme for generating frequency-modulated continuous-wave (FMCW) signals with broad bandwidth. In such a master-slave system, a semiconductor laser under current modulation with single-tone electrical signal is taken as the master laser (ML), and its output optical signal with modulated power is injected into another semiconductor laser (taken as the slave laser, SL) for generating FMCW. The simulated results show that, under suitable operating condition, the bandwidth and the sweep rate of generated FMCW signal can reach 15.4 GHz and 4.83 GHz/ns, respectively. Through further introducing optoelectronic feedback into SL for suppressing the phase noise, the contrast of the frequency comb in the FMCW signal can be increased by 20.22 dB.

Three products based on VCSEL chips are developed for intelligent driving Lidar and driver monitor system. The line beam products used for long-distance detection achieved a 0.1°horizontal divergence angle, 23° vertical divergence angle, and the vertical beam uniformity more than 80%. For the area beam products used in medium and short distance detection, has achieved the field of view 125°×25°. For the super wide field of view area beam product, can applied in driver monitor system, the FOV is 160°×120°. These three products all have excellent performance in a wide temperature range (- 40 degrees centigrade ~ 110 degrees centigrade).

We demonstrate a hybrid integrated laser with nearly two folds of direct modulation bandwidth enhancement and 150 folds of linewidth reduction, by introducing the photon-photon resonance effect and self-injection locking effect to a commercial DFB laser simultaneously through an external high-Q silicon nitride microring reflector (MRR). Different from the widely studied passive feedback lasers, the proposed high-Q MRR keeps the DFB laser in the strong self-injection locking state, which can achieve stable narrow linewidth single-mode output with high Side-Mode Suppression Ratio. After packaging the proposed hybrid laser, we measure its direct modulation bandwidth and linewidth, which are increased from 7.70GHz to 15.28GHz, and reduced from 600kHz to 4kHz, respectively. This work explores a compact footprint and low-cost modulation bandwidth enhancement and linewidth reduction scheme for many applications such as high-speed coherent optical communication and microwave photonics.

A hybrid integrated tunable narrow-linewidth laser is demonstrated in this paper. The hybrid laser comprises a commercial DFB laser butt-coupled to an external cavity with a micro-ring resonator. A transfer matrix model has been presented and the wavelength performance of the laser has been analyzed. In the experiment, the hybrid laser Lorentzian linewidth is ~5KHz and the tuning range is ~2.75 nanometer.

We report a compact and robust laser linewidth reduction solution for commercially available distributed feedback (DFB) semiconductor lasers by butt-coupling a high-Q Si₃N₄ microring reflector to a DFB semiconductor laser. We fabricate the microring reflector on the 80nm-thick high-aspect-ratio Si3N4 waveguide platform. The 3-dB bandwidth and the free spectral range of the fabricated Si₃N₄ microring reflector are measured to be 50 MHz and 14.13 GHz, respectively, corresponding to a Q factor of over 3.8 million and finesse of 283. In the experiment, the intrinsic linewidth of the hybrid integrated laser is reduced to an ultra-low level of 2.86 Hz. The proposed hertz-linewidth hybrid integrated laser has great potentials in high-speed coherent optical communications systems and high-resolution optical metrology.

A novel laser phase noise measurement method based on self-homodyne structure with a Faraday rotating mirror (FRM) and an optical coherent receiver is proposed and experimentally demonstrated. The proposed method is simple in structure and easy to operate. Compared with the ordinary phase noise measurement system of self-homodyne optical coherent receiver, the length of the required delay fiber is halved and the polarization of the optical signal is more stable. Experimental results show that the proposed method can accurately characterize the phase noise and the linewidth of the laser under test, which are consistent with those obtained by the conventional self-homodyne method.

Electroabsorption-modulated laser (EML) is integrated by distributed feedback (DFB) laser and electro-absorption modulator (EAM). Microwave interaction in the EML has been observed to limit modulation performance especially in high frequency region. In this work, the EML is investigated as a three-port network with two electrical inputs and one optical output. Scattering matrix of the device was derived theoretically and obtained experimentally. Thus, microwave equivalent circuit model of the EML can be established and microwave interaction between the DFB laser and the EAM was successfully extracted. The results reveal that microwave interaction within an integrated EML contains both electrical isolation and optical coupling. The electrical isolation is bidirectional while the optical coupling is directional, which aggravates the performance of the EML. This result can provide a reference for further device optimization design.

Shrinking optical components and systems without compromising performance has been a challenge. New sensors and components are developing the methodology in research advanced multiple configuration systems. The effect of system evaluated criteria that Modulation Transfer Function (Modulation Transfer Function, the MTF), Energy concentration (Radial Energy Analysis, REA), diffusion (Spot Diagram, RMS) can support our issue qualitatively. Results showed that can not only change systems weight, size and structural stability, but also increase freedom in these kinds design.

Modified rate-equations model for a multi-mode semiconductor laser locked to the high-Q microresonator taking Bogatov effect into account is developed. The effects of the symmetric and asymmetric mode interactions are shown.