This PDF file contains the front matter associated with SPIE Proceedings Volume 10559, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

We present and demonstrate a unique type of secure key distribution utilizing ultra-long fiber laser (UFL). A 500km long secure key distribution link based on Raman gain UFL is demonstrated experimentally. An error-free distribution of a random key with an average bit-rate of 100Hz between the users is demonstrated and the key is shown to be unrecoverable to an eavesdropper employing either time or frequency domain passive attacks.

Broadband access in optical domain usually focuses in providing a pervasive cost-effective high bitrate communication in a given area. Nowadays, it is of utmost interest also to be able to provide a secure communication to the costumers in the area. Wireless access networks rely on optical domain for both fronthaul and backhaul of the radio access network (C-RAN). Multicore fiber (MCF) has been proposed as a promising candidate for the optical media of choice in nextgeneration wireless. The capacity demand of next-generation 5G networks makes interesting the use of high-capacity optical solutions as space-division multiplexing of different signals over MCF media. This work addresses secure MCF communication supporting C-RAN architectures. The paper proposes the use of one core in the MCF to transport securely an optical quantum key encoding altogether with end-to-end wireless signal transmitted in the remaining cores in radio-over-fiber (RoF). The RoF wireless signals are suitable for radio access fronthaul and backhaul. The theoretical principle and simulation analysis of quantum key distribution (QKD) are presented in this paper. The potential impact of optical RoF transmission crosstalk impairments is assessed experimentally considering different cellular signals on the remaining optical cores in the MCF. The experimental results report fronthaul performance over a four-core optical fiber with RoF transmission of full-standard CDMA signals providing 3.5G services in one core, HSPA+ signals providing 3.9G services in the second core and 3GPP LTEAdvanced signals providing 4G services in the third core, considering that the QKD signal is allocated in the fourth core.

Entangled photon pairs are created by a system consisting of a 1064 nm pump diode laser that is fiber coupled to a high generation rate photon pair source. The source is a dual element periodically poled potassium titanyl phosphate (KTP) waveguide that up-converts 1064 nm photons to single 532 nm photons in the first stage. In the second stage, the green photons are down converted to energy entangled photon pairs at 800 nm and 1600 nm. The output photon pairs are guided by fiber to sorting optics where they are separated and sent into high-efficiency photon detectors. In particular, the 1600 nm photons are detected by a superconducting nanowire with efficiency over 60% and dead time less than 50 ns. Detector output electrical signals are sent to a time tagger with bin resolution as narrow as 25 ps for coincidence counting. The ultimate goal of this setup is to demonstrate a singlesource, high efficiency, high data rate, quantum communication system to enable Earth-space quantum networks. Of particular interest is a source of entangled photons that is amenable to utilization in aircraft and spacecraft under rigorous flight and environmental conditions. Test results that characterize the entangled photon pair creation and detection capabilities of our system will be presented.

Modern networks implement multi-layer encryption architecture to increase network security, stability, and robustness. We developed a new paradigm for optical encryption based on the strengths of optics over electronics and according to temporal optics principles. We developed a highly efficient all-optical encryption scheme for modern networks. Our temporal encryption scheme exploits the strength of optics over electronics. Specifically, we utilize dispersion together with nonlinear interaction for mixing neighboring bits with a private key. Our system encrypts the entire network traffic without any latency, encrypt the signal itself, exploit only one non- linear interaction, it is energetically efficient with low ecologic footprint, and can be added to current networks without replacing the hardware such as the lasers, the transmitters, the routers, the amplifiers or the receivers. Our method can replace current slow encryption methods or can be added to increase the security of existing systems. In this paper, we elaborate on the theoretical models of the system and how we evaluate the encryption strength with this numerical tools.

Quantum Key Distribution (QKD) is attracting much interest for the distribution of cryptographic keys using single photon signals. Currently QKD is often used to provide secure distribution of cryptographic keys for the encryption of data transmitted using conventional classical communication systems. This paper reports major field trials carried out over several months on the Cambridge UK Quantum Network showing the operation of QKD systems alongside high-speed classical transmission systems encrypted QKD derived with AES keys. Quantum Key transmission at record secure key rates of 3.3Mbps, 3.2Mbps and 2.5Mbps has been achieved over 5km, 9.5km and 10.5km long links respectively with corresponding average Quantum bit error rates (QBER) of 2.9%, 2.4% and 3%. Using a 33km link attached to the network with a loss of 7.5 dB, a secure key rate of 1.4 Mbps is achieved with an average QBER of 3.4%. Under loop back conditions this link provides a 66 km transmission path with a 16dB fibre loss, enabling a field trial using the QKD signals multiplexed with two wavelengths each transmitting 100Gb/s classical data to be carried out. This achieves an average secure key rate of 80.2 kbps and a mean QBER of 6.6%, in line with theoretical predictions. During the trial duration, the statistics of the QBER were found to be Gaussian distributed with a standard deviation of 0.5. The results of the field trial suggest that the system works stably and has considerable potential for applications in metropolitan networks. Further measurements will be reported at the conference.

A novel optical encryption technique that uses oscillations on a liquid lens surface and random phase masks to encode images is presented. Excited liquid surface patterns can encode optical wave fronts, making the optical transfer function of the system a function of time. This allows for possible protection against known and chosen plaintext attacks and potentially enables more flexible realizations of random phase mask security systems. However, the periodic nature of liquid surface oscillations and the geometry of the patterns can potentially place constraints on the efficacy of such a system. Simulation results show that the entropy of encrypted images depends on the liquid surface mode shape and the recording duration of the encrypted image. Additionally, it is shown that mistiming the liquid system during decryption gives significant error in the recovered images. The simulations presented here use a model of a commercial available liquid lens, giving the possibility for future comparison with experimental results.

One of important applications in 5G mobile communications is the enhanced mobile broadband (eMBB). A promising approach for achieving 5G eMBB under the limited radio bandwidth and energy is an introduction of a small-cell structured network. An advanced utilization of multi-input multi-output (MIMO) transmission is also another possible approach. First, the conceptual structure of distributed MIMO network is introduced. A number of distributed antennas (DAs) are deployed over a macro-cell area and they are connected to a macro-cell base station (MBS) via optical mobile fronthaul. Then, we present the recent advances in distributed MIMO cooperative transmission, i.e., space-time block coded transmit diversity (STBC-TD) for improving the link capacity of a macro-cell edge area, minimum mean square error multiuser multiplexing combined with singular value decomposition (MMSE-SVD) for increasing the sum capacity, and blind selective mapping (SLM) for reducing the transmit signal peak-to-average power ratio (PAPR).

We have carried out research and development of next generation (5G) wireless communication systems in dense user environments utilizing advanced photonic technologies. Especially, we have focused on a heterogeneous wireless communication system, which includes 4G, 3G, WiFi and millimeter-wave wireless links, with broadband, low latency, low-power consumption and low-cost. In this report, photonic-based millimeter-wave wireless links of ultra-small cells (atto-cells) in a big football stadium are discussed. Advantages of an asymmetric millimeter-wave link combined with terminal localization techniques are also pointed out. Some basic experimental results on the millimeter-wave wireless links in an actual big football stadium are also reported.

Analog optical fronthaul for 5G network architectures is currently being promoted as a bandwidth- and energy-efficient technology that can sustain the data-rate, latency and energy requirements of the emerging 5G era. This paper deals with a new optical fronthaul architecture that can effectively synergize optical transceiver, optical add/drop multiplexer and optical beamforming integrated photonics towards a DSP-assisted analog fronthaul for seamless and medium-transparent 5G small-cell networks. Its main application targets include dense and Hot-Spot Area networks, promoting the deployment of mmWave massive MIMO Remote Radio Heads (RRHs) that can offer wireless data-rates ranging from 25Gbps up to 400Gbps depending on the fronthaul technology employed. Small-cell access and resource allocation is ensured via a Medium-Transparent (MT-) MAC protocol that enables the transparent communication between the Central Office and the wireless end-users or the lamp-posts via roof-top-located V-band massive MIMO RRHs. The MTMAC is analysed in detail with simulation and analytical theoretical results being in good agreement and confirming its credentials to satisfy 5G network latency requirements by guaranteeing latency values lower than 1 ms for small- to midload conditions. Its extension towards supporting optical beamforming capabilities and mmWave massive MIMO antennas is discussed, while its performance is analysed for different fiber fronthaul link lengths and different optical channel capacities. Finally, different physical layer network architectures supporting the MT-MAC scheme are presented and adapted to different 5G use case scenarios, starting from PON-overlaid fronthaul solutions and gradually moving through Spatial Division Multiplexing up to Wavelength Division Multiplexing transport as the user density increases.

5G systems are supposed to support coexistence of multiple services such as ultra reliable low latency communications (URLLC) and enhanced mobile broadband (eMBB) communications. The target of eMBB communications is to meet the high-throughput requirement while URLLC are used for some high priority services. Due to the sporadic nature and low latency requirement, URLLC transmission may pre-empt the resource of eMBB transmission. Our work is to analyze the URLLC impact on eMBB transmission in mobile front-haul. Then, some solutions are proposed to guarantee the reliability/latency requirements for URLLC services and minimize the impact to eMBB services at the same time.

The high-speed train in Japan connects megalopolises through many tunnels or underground routes. To provide seamless internet connectivity to the hundreds of passengers on the train, a new backhaul communication system is proposed in a millimeter-wave band by Radio over Fiber. We have shown that a vector-modulated signal can be generated by multiplying the radio frequency in the optical domain to avoid effects of chromatic dispersion in an optical fiber. In this paper, we show characteristics of long distance transmission by Radio over Fiber. Also, we present our concept and report on the relationship between the symbol rate and the modulation accuracy of the 96 GHz band signal generated by frequency doubling using RoF.

We have determined the optimal beams for free-space optical transmission through atmospheric turbulence. These are stochastic eigenmodes derived analytically from a canonical turbulence model, assuming known turbulence statistics. Under weak or strong turbulence, using these modes as transmit and receive bases minimizes signal degradation by turbulence, and minimizes the complexity of any signal processing method employed to compensate for turbulence. These modes can be mapped to/from single-mode waveguides by fundamentally lossless modal multiplexers and demultiplexers. Adaptive optics can be replaced by adaptive multi-input multi-output signal processing, enabling compensation of fast fluctuations of both phase and amplitude.

Light emitting diodes - LEDs are modernizing the indoor illumination and replacing current incandescent and fluorescent lamps rapidly. LEDs have multiple advantages such as extremely high energy efficient, longer lifespan, and lower heat generation. Due to the ability to switch to different light intensity at a very fast rate, LED has given rise to a unique communication technology (visible light communication - VLC) used for high speed data transmission. By studying various kinds of commonly used VLC channel analysis: diffuse and line of sight channels, we presented a simply improved indoor and intra-vehicle visible light communication transmission model. Employing optical wireless communications within the vehicle, not only enhance user mobility, but also alleviate radio frequency interference, and increase efficiency by lowering the complexity of copper cabling. Moreover, a solution to eliminate ambient noise caused by environmental conditions is examined by using optical differential receiver. The simulation results show the improved received power distribution and signal to noise ratio - SNR.

Recently, free-space optical (FSO) networks have been investigated as a potential replacement for traditional WiFi networks due to their large bandwidth potentials. However, FSO networks often suffer from a lack of mobility. We present a hybrid free-space optical and radio frequency (RF) system that we have named WiFO, which seamlessly integrates free-space optical links with pre-existing WiFi networks. The free-space optical link in this system utilizes infrared LEDs operating at a wavelength of 850nm and is capable of transmitting 50Mbps over a three-meter distance. In this hybrid system, optical transmitters are embedded periodically throughout the ceiling of a workspace. Each transmitter directs an optical signal downward in a diffuse light cone, establishing a line of sight optical link. Line of sight communications links have an intrinsic physical layer of security due to the fact that a user must be directly in the path of transmission to access the link; however, this feature also poses a challenge for mobility. In our system, if the free-space optical link is interrupted, a control algorithm redirects traffic over a pre-existing WiFi link ensuring uninterrupted transmissions. After data packets are received, acknowledgments are sent back to a central access point via a WiFi link. As the demand for wireless bandwidth continues to increase exponentially, utilizing the unregulated bandwidth contained within optical spectrum will become necessary. Our fully functional hybrid free-space optical and WiFi prototype system takes full advantage of the untapped bandwidth potential in the optical spectrum, while also maintaining the mobility inherent in WiFi networks.

We are seeing a growing use of light emitting diodes (LEDs) in a range of applications including lighting, TV and backlight board screen, display etc. In comparison with the traditional incandescent and fluorescent light bulbs, LEDs offer long life-space, much higher energy efficiency, high performance cost ratio and above all very fast switching capability. LED based Visible Light Communications (VLC) is an emerging field of optical communications that focuses on the part of the electromagnetic spectrum that humans can see. Depending on the transmission distance, we can divide the whole optical network into two categories, long haul and short haul. Visible light communication can be a promising candidate for short haul applications. In this paper, we outline the configuration of VLC, its unique benefits, and describe the state of the art research contributions consisting of advanced modulation formats including adaptive bit loading OFDM, carrierless amplitude and phase (CAP), pulse amplitude modulation (PAM) and single carrier Nyquist, linear equalization and nonlinear distortion mitigation based on machine learning, quasi-balanced coding and phase-shifted Manchester coding. These enabling technologies can support VLC up to 10Gb/s class free space transmission.

In the last decade data centers have become a crucial element in modern human society. However, to keep pace with internet data rate growth, new technologies supporting data center should develop. Integration of optical wireless communication (OWC) in data centers is one of the proposed technologies as augmented technology to the fiber network. One implementation of the OWC technology is deployment of optical wireless transceiver on top of the existing cable/fiber network as extension to the top of rack (TOR) switch; in this way, a dynamic and flexible network is created. Optical wireless communication could reduce energy consumption, increase the data rate, reduce the communication latency, increase flexibility and scalability, and reduce maintenance time and cost, in comparison to extra fiber network deployment. In this paper we review up to date literature in the field, propose an implementation scheme of OWC network, discuss ways to reduce energy consumption by parallel link communication and report preliminary measurement result of university data center environment.

In this paper, we have proposed a novel modulation scheme for visible light communication (VLC), that has two preprocessing blocks namely, discrete Fourier transform (DFT) block and frequency domain signal shaping block, prior to conventional optical-orthogonal frequency division multiplexing (O-OFDM) modulation. Two variants of proposed scheme namely, with and without DC have been implemented so as to make it compatible with intensity modulation and direct detection (IM/DD). The results of the proposed schemes are compared against their standard O-OFDM counterparts based on peak-to-average power ratio (PAPR) and symbol error rate (SER). Results show that the proposed scheme has significantly lower PAPR and better SER as compared to corresponding O-OFDM counterpart.

Visible Light Communications (VLC) receivers adapted to be used in high transmission rates will eventually use either, high aperture lenses or non-linear optical elements capable of converting light arriving to the receiver into an electric signal. The high aperture lens case, reveals a challenge from an optical designers point-of-view. As a matter of fact, the lens must collect a wide aperture intensity flux using a limited aperture as its use is intended to portable devices. This last also limits both, lens thickness and its focal length. Here, we show a first design to be adapted to a VLC receiver that take these constraints into account. This paper describes a method to design catadioptric and monolithic lenses to be used as an optical collector of light entering from a near point light source as a spherical fan L with a wide acceptance angle α◦ and high efficiency. These lenses can be mass produced and therefore one can find many practical applications in VLC equipped devices. We show a first design for a near light source without magnification, and second one with a detector’s magnification in a meridional section. We utilize rigorous geometric optics, vector analysis and ordinary differential equations.

In this paper, we propose bend insensitive fiber designs that can meet both the bend loss and mechanical reliability needs for silicon photonic packaging. To improve the bend loss, we adopt profile designs with a low index trench that allow us to reduce the bending loss while keeping the mode field diameter compatible with the standard single mode fiber. To improve the mechanical reliability, we put a Titania-doped glass layer on the surface of the fiber cladding, which improves the fiber reliability under tight bending conditions. We describe both the core and Titania layer designs and present results on fiber optical and mechanical performances.

As the 5G standardization is underway, it has become apparent that the existing wireless fronthaul network needs to be redesigned in order to meet the future requirements. Passive optical network, with a shared fiber infrastructure, is an excellent candidate for 5G fronthaul transport. The 3GPP will complete the 5G New Radio standard in Release 15 by June 2018. The ITU-T Q2/SG15 group initiated the G.Sup.5GP project in June 2017 to study how 5G fronthaul requirements can be best supported by passive optical network. Many other standards development organizations have also been working on 5G transport standards, but their views are not yet fully aligned. The purpose of this paper is therefore not to provide a conclusion, but to report the recent progress in 5G related standards; to evaluate WDM and TDM based PON for 5G fronthaul, and to discuss the challenges ahead.

Converged Fiber-Wireless (FiWi) broadband access network proves to be a promising candidate that is reliable, robust, cost efficient, ubiquitous and capable of providing huge amount of bandwidth. To meet the ever-increasing bandwidth requirements, it has become very crucial to investigate the performance issues that arise with the deployment of next-generation Passive Optical Network (PON) and its integration with various wireless technologies. Apart from providing high speed internet access for mass use, this combined architecture aims to enable delivery of high quality and effective e-services in different categories including health, education, finance, banking, agriculture and e-government. In this work, we present an integrated architecture of 10-Gigabit-capable PON (XG-PON) and Enhanced Distributed Channel Access (EDCA) that combines the benefits of both technologies to meet the QoS demands of subscribers. Performance evaluation of the standards-compliant hybrid network is done using discrete-event Network Simulator-3 (NS-3) and results are reported in terms of throughput, average delay, average packet loss rate and fairness index. Per-class throughput signifies effectiveness of QoS distribution whereas aggregate throughput indicates effective utilization of wireless channel. This work has not been reported so far to the best of our knowledge.

Multi-core fiber transmissions provide great capacity scalability for future optical backbone and access networks. Unfortunately, the polarization-mode dispersion has not been experimentally investigated so far in single-mode multi-core fibers. In this scenario, the differential group delay may present a time-varying nature in each core because of the temporal fluctuations of the optical medium. In order to investigate this phenomenon, we present a coupled-mode theory based on local modes to simulate numerically the polarization-mode dispersion in such optical media and we report extensive experimental measurements of the time-varying differential group delay using a homogeneous 4-core multi-core fiber considering three different months. Our results indicate that the differential group delay presents a similar, but not identical, temporal evolution in the four cores.

Millimeter-wave radar technology in a frequency band of 96 GHz is promising to detect small objects with a high range resolution because of its short wavelength and broadness of available bandwidths of 8 GHz. However, transmission distance in the millimeter-wave bands is limited by high atmospheric attenuation. Radio over fiber (RoF) technology should be implemented to transport these millimeter-wave signals to remote radar heads via an optical fiber network. In the study, we discuss the RoF network for distributed radar systems in the millimeter-wave and submillimeter-wave bands.

We summarize the enabling technologies for broadband millimeter-wave communication at W-band. These enabling technologies include photonics-aided broadband signal generation, high-spectral efficiency modulation format, multiple-input multiple-output (MIMO) reception, high gain antenna, optical and electrical multi-carrier modulation, antenna polarization multiplexing and multi-band multiplexing, advanced digital signal processing (DSP), and heterodyne detection. Based on these advanced technologies, we have realized over 400G wireless signal transmission and over 2.5-km wireless delivery with a bit rate up to 50Gb/s at W-band.

The conventional visible light (VL) communication signals based on the LED array and photodiode severely decreases at the far away receiving point in the VL channel by the path loss effect and the insufficient compensation capability of the receiver. In this paper, we consider the wide-range VL communication technique that the compensation extent of the path loss distortion provides in advance by threshold map, and the optimal receiver circuit with compensation utilizes for VL communication.

The radio over fiber (RoF) relay scheme can contribute to solving the radio wave blind area problem and improving cell edge performance in 5G mobile communications. However, RoF relay system requires many pairs of optical fiber link or Tx/Rx unit in case of MIMO system. To reduce complexity and cost of RoF relay system, we propose a novel relay system using STBC (space-time block coding) and MRC (maximum rate combination) scheme. In this research, we demonstrate a basic experimental using WiMAX base station and show some simulation results.

Visible light communications (VLC) based on intensity-modulation with direct-detection (IM/DD) is a promising technology to offer broadband wireless Internet access. A VLC system based on the well-known multi-carrier orthogonal frequency-division multiplexing (OFDM) modulation has the potential to coexist with radio frequency (RF) technologies such as WiFi. Recently, the VLC technology is considered to enable wireless connectivity of resource limited devices, thus enabling the Internet-of-Things (IoT) vision. This paper presents a novel concept for modulating multiple light sources to realize a lightweight version of OFDM communication chain suitable for resource limited IoT devices. In such proposed system, different sinusoidal streams from an array of light sources are carrying the encoded OFDM time-domain samples, thus enabling the realization of the Fourier transformation in the optical domain. Accordingly, the fast Fourier transform (FFT) operation required for the demodulation at the receiver side is eliminated, which is crucial for resource limited IoT devices. In addition, the proposed concept, (1) offers the same spectral efficiency as the well-known asymmetrically clipped optical OFDM (ACO-OFDM), (2) reduces the bandwidth requirement from individual light sources, (3) reduces the peak-to-average power ratio (PAPR) of the signal formed and transmitted over the optical channel, and (4) supports simultaneous sensing applications using the different sinusoidal streams that are acting as unique beaconing signals. The proposed concept is numerically evaluated and compared with ACO-OFDM. The obtained results reveal a clear reduction in the PAPR with ∼ 5dB at a complementary cumulative distribution function (CCDF) of 10⁻² and remarkable enhancement in bit-error performance.

A position-multiplexing technique with ultra-broadband illumination is proposed to enhance the information security of an incoherent optical cryptosystem. The simplified optical encryption system only contains one diffuser acting as the random phase mask (RPM). Light coming from a plaintext passes through this RPM and generates the corresponding ciphertext on a camera. The proposed system effectively reduces problems of misalignment and coherent noise that are found in the coherent illumination. Here, the use of ultra-broadband illumination has the advantage of making a strong scattering and complex ciphertext by reducing the speckle contrast. Reduction of the ciphertext size further increases the strength of the ciphering. The unique spatial keys are utilized for the individual decryption as the plaintext locates at different spatial positions, and a complete decrypted image could be concatenated with high fidelity. Benefiting from the ultra-broadband illumination and position-multiplexing, the information of interest is scrambled together by a truly random method in a small ciphertext. Only the authorized user can decrypt this information with the correct keys. Therefore, a high performance security for an optical cryptosystem could be achieved.