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The performances of OPSquare flat data-center network based on flow-controlled optical switches are investigated. Results show

We analysed the space coding scheme applied to the space division multiplexing transmission in two types of multicore fibres with different intercore crosstalk. Rather than the usual optical multiple-input and multiple-output processing, simple space coding based on optical code division multiplexing was used to achieve separate detection of the desired signals. The signal to interference-and-noise ratio has a positive value when the relative phase drift between the optical signals in different cores is suppressed to values typically less than ∼π/10. Although a complete solution of the phase drift control problem was not achieved, this scheme suggests that real-time MCF transmissions are possible.

A novel FOCI lens system was designed in our AOC optical engines for data transmissions at 10Gbps and 25Gbps. This design can be applied to AOC types such as USB3.0, 10G SFP+AOC and 40G QSFP+AOC.

50 and 25 Gbaud Nyquist QPSK signals are converted to Nyquist-WDM signals with half baud-rate, by using a phase modulator and an optical Nyquist filter. The EVM were 9% after the conversion employing duo-binary filter.

Dual-carrier SD-FEC gain sharing is utilized as a nonlinearity mitigation strategy for coherent super-channels in the context of submarine communications. Up to 0.68 dB benefit in Q and 50% more capacity is demonstrated.

Increasing line rates beyond 56Gb/s is a big challenge for transceiver front-ends. We discuss recent developments towards 100Gb/s copper, +56Gb/s multi-channel single-mode VCSEL links and segmented MZM drivers for advanced modulation.

We experimentally demonstrate a single-carrier 400G solution based on 51.25-GBaud PDM-32QAM signal at 6.15-b/s/Hz SE over 1200-km transmission distance. Training assisted pre-compensations and both transmitter and receiver based look-up table are employed to mitigate channel bandwidth constraint and component nonlinearity impairment.

An OSNR-aware adaptive optical transmission system using time-division-multiplexed pilot sequences is proposed. We successfully demonstrated that the system automatically optimizes signal form by using in-band OSNR estimation and a bidirectional feedback channel in filed-installed fiber.

We demonstrate an all-electronically multiplexed, single optical carrier, flexible rate transmitter based on a high-speed 3-bit multiplexer and analog-to-digital converter integrated circuit. Line rates up to 1.08 Tb/s are obtained using 90 Gbd PDM-64QAM.

All-optical signal processing has been considered a solution to overcome the bandwidth and speed limitations imposed by conventional electronic-based systems. Over the last few years, an impressive range of all-optical signal processors have been proposed, but few of them come with reconfigurability, a feature highly needed for practical signal processing applications. Here we propose and experimentally demonstrate an analog optical signal processor based on a phase-shifted distributed feedback semiconductor optical amplifier (DFB-SOA) and an optical filter. The proposed analog optical signal processor can be reconfigured to perform signal processing functions including ordinary differential equation solving and temporal intensity differentiation. The reconfigurability is achieved by controlling the injection currents. Our demonstration provitdes a simple and effective solution for all-optical signal processing and computing.

We propose a PDM-DD-SSB-OFDM system with a single-end PD at the receiver and a reduced guard band for short reach communications. The receiver sensitivity is −11.8dBm for the 100-Gbit/s-PDM-DD-SSB-OFDM system.

This paper presents the simultaneous transmission of millimeter-wave and terahertz-wave radio signals over an optical fiber and air by a single optical frequency comb source with several types of receiver configurations.

We propose and experimentally demonstrate novel optical transceiver that enables accommodation of multiple services having diverse requirements within the bandwidth of the single transceiver by a holistic SNR optimization of signal assigned for each service.

We report a novel single-lane 112-Gbps system based on SFP module with 10km SSMF reach employing a duobinary 4-PAM modulation. Impairment caused by electrical circuit is compensated by digital pre-distortion techniques.

We review technology advancement in our three generations of coherent DSP implemented with 40, 20, and 16-nm CMOS technologies. The latest 16-nm implementation achieves sub-10-watt per 100 Gb/s transport for emerging data-center interconnect application.

We discuss dynamic optical waveform generation using line-by-line coherent modulation of optical frequency combs, and arbitrary spatial beam forming utilizing 2D/3D photonic integrated circuits. Free-space optical communications and electronic warfare applications will also be discussed.

An optical inter-channel interference mitigation approach for wavelength-overlapped channels with combinations of different baud rates and pulse shapes is experimentally demonstrated. The robustness of this approach is verified by OSNR improvements under distinct system configurations.

An adaptive digital pre-distortion method to enable single carrier 400G DP-128QAM transmission over 328 km fiber with 30% FEC is presented. Experimental comparison in reach and spectral efficiency is made with 400G DP-64QAM.

Nyquist-mPPM-QPSK modulation format is proposed with high power efficiency and doubled spectrum efficiency compared with mPPM-QPSK, in particular, a 1.3dB power efficiency advantage over QPSK using Nyquist-4PPM-QPSK is demonstrated under the same spectrum efficiency.

We propose a ROADM structure based on low-modal-crosstalk FMF and mode MUX/DEMUX, in which both mode and wavelength can be added/dropped independently without MIMO DSP. We experimentally demonstrate its feasibility over 11.8-km 2-mode FMF.

□Long-haul, Metro and Data-centre networks □Coherent / Direct-detection □Modulation techniques □Pulse Amplitude Modulation □Discrete Multi-Tone (DMT) □Coherent Transceivers □Compensation methods □Analogue Filters □Digital Filters □MLSE □Final thoughts.

We show that the impact of non-ideal time synchronization between in-phase and quadrature electrical signals can be critical in multi-subcarrier systems. We propose the use of an 8×8 real-valued butterfly equalizer structure to mitigate it.

We present DSP enabled advanced modulation techniques for 100G per lambda data center optical modules based on low cost and power efficient directly modulated laser transmitters and single photodiode direct detection receivers.

We report a hardware optimization for frequency and phase recovery algorithms based on Mth-order power schemes, evaluating the accuracy of the reported architecture with an 8-bit DSP in real-time for a 1.25 and 2.5 Gb/s DQPSK signal.

We demonstrate a SDM-TWDM-PON system with 700-Gb/s and 280-Gb/s aggregated capacity for the downstream and upstream directions respectively. 20-km seven-core fibre is employed to support 100G/40G TWDM-PON per core based on 10G-class optical components with optical equalization.

We propose a novel optical label switching OADM prototype with nanoseconds reconfiguration and power-equalization time. System demonstration shows dynamic add/drop operation with

We demonstrate a wideband OFDM transmission, using electrical IQ-mixing and signal combining. Transmission rates of 154.9 Gb/s over 2 km of SSMF were achieved with an IM/DD system on a single wavelength and a single polarization.

We report a 8.96 Tb/s transmission over 20×75 GHz channels, using 56-GBd 16QAM signals with 1.14 samples-per-symbol Nyquist pulses. Wideband and spectrally-sliced optical receivers' performance is compared, yielding 1500 and 1250 km transparent reach, respectively.

A novel optical superchannel protection scheme is proposed and successfully demonstrated over field fiber links for 400G capacity using main 400G DP-16QAM and protection 400G DP-QPSK superchannels together with in-service OTDR fault localization.

We have experimentally demonstrated real-time symmetric 100G-PON based on 10 G-class optical devices supporting 0–20 km SMF transmission without DSP. Optical dispersion compensator is employed to equalize the limited bandwidth of the system.

We investigated the performance of symmetrical optical amplified 40 Gbps TDM-PON using only 10G class optics by means of DSP. We also applied DSP techniques to improve the recovery of burst mode upstream signal.

The performances of different fast chromatic dispersion estimation (CDE) techniques are compared. Then a PMD robust CDE technique with lower computation complexity and better universality is proposed. Simulation and experimental results are presented.

We present a review of direct detection systems with focus on the evolution of the dimensionality of formats and their underlying transmitter and receiver architectures.

This study describes partial multiflow functionality enabling substantial saving of transceiver resources while avoiding complex add/drop stage needed for full multiflow feature.

Novel optical fiber designs are currently investigated to enable optical communication links with higher capacity and bandwidth density. In this paper, we discuss the prospects and challenges of ring core fibers for MIMO-free transmissions over multiplexed spatial channels.

Today, the demand for high-speed data communication and mobile communication has exploded. Thus, there is a growing need for optical communication systems that convert large volumes of data to optical signals and that accommodate and transmit the signals across long distances. Digital optical communication with these characteristics consists of a master unit (MU) and a slave unit (SU). However, the digital optical units that are currently commercialized or being developed transmit data without compression. Thus, digital optical communication using these units is restricted by the quantity of optical frames when adding diversity or operating with various combinations of CDMA, WCDMA, WiBro, GSM, LTE, and other mobile communication technologies. This paper suggests the application of a data compression algorithm to a digital signal processor (DSP) chip as a field programmable gate array (FPGA) and a complex programmable logic device (CPLD) of a digital optical unit to add separate optical waves or to transmit complex data without specific changes in design of the optical frame.

An integrated photoconductive (PC) sensor is proposed and tested as a fundamental extension of the semiconductor switch. An enhanced field-of-view (FOV) is demonstrated for application to indoor optical wireless communications (OWC). The three-fold symmetric architecture of the corner-cube PC sensor is adapted for use with the dc-shifted ac-three-phase $({\rm ac}_{3\phi})$ to establish output photocurrent characteristics that are largely independent of the incident optical angle-of-arrival. An enhanced FOV of $60^{\circ}\times 40^{\circ}$ is demonstrated. The device can be integrated in future OWC systems for increased channel redundancy and greater reliability.

We have demonstrated a novel coherent optical detection architecture that serves as a matched filter and successfully discriminates between various encoded optical waveforms with high confidence. The waveforms are produced by encoding the spectral phase of an optical frequency comb with codes from a Walsh-Hadamard set. The encoded optical waveforms are decoded with a coherent detection technique implemented using an optical frequency comb as a set of local oscillators, an interferometer, and a pair of differential balanced photodetectors. The use of only linear optical devices in the receiver results in a higher sensitivity compared to the use of nonlinear optical thresholding and gating techniques. Decoding is demonstrated at power levels of ~ 25 μW, which are much lower than previously reported. Possible applications of the receiver architecture include laser radar and optical communications in an optical code-division multiple access network.

The plain old telephone service, POTS, still generates the largest proportion of public network operators' revenues. If optical communications systems are to compete with traditional twisted-pair copper systems in delivering telephony, they must achieve the same levels of cost and service availability, offer low-risk investment in optical fiber infrastructure, and satisfy the same regulatory requirements. Interferometic optical communications system can meet these requirements, in which the laser in the CPE is replaced by an interferometer for the outgoing voice channel, and part of the received optical power is converted to electrical power using photovoltaic cells and an energy storage device to drive the CPE. The reach of the system is similar to locally powered laser systems in the downstream direction, but back reflections and scattering can affect the upstream link if the communications and powering signals share the same path.

In this article we present an all passive optical iterative interference cancellation method for optical CDMA. We propose the receiver structure based on advanced binary optical logic gates (ABOLGs). Since the performance bottleneck in optical communication systems is the conversion from optical to electronic domains for optical detectors, the interference cancellation has been performed in the optical domain. In incoherent optical communication systems, we have only the positive values for the optical signals. In the proposed system, we bypass the negative values using logic arrays. In the simulations we consider multiple access interference and neglect other sources of noise. Simulation results show that in the future optical systems, the interference can be eliminated completely using iterative methods in the optical domains.

End-to-end real-time optical orthogonal frequency-division multiple-access (OOFDMA) passive optical networks (PONs) with adaptive dynamic bandwidth allocation (DBA) and colorless optical network units (ONUs) are experimentally demonstrated, for the first time, at aggregated 10.375 Gb/s over 26.4 km standard single-mode fibers based on intensity modulation and direct detection. The colorless ONU operation for several representative wavelengths across the C-band is successfully achieved by utilizing cost-effective reflective semiconductor optical amplifier intensity modulators, whose narrow signal modulation bandwidths are fully exploited through adaptability of the OOFDM transceivers and adaptive DBA. Taking into account the optical beat interference effect, the impact of wavelength spacing between adjacent ONUs on the upstream OOFDMA PON performance is experimentally investigated, based on which the minimum achievable ONU wavelength spacing is identified.

We propose a multichannel optical microwave system employing a frequency up-converting optoelectronic oscillator (FU-OEO) [FU-OEO: frequency up-converting optoelectronic oscillator] as a low-phase noise local oscillator (LO) and a multichannel frequency up-converter. Employing the FU-OEO, we demonstrated an optical microwave system capable of 16 optical microwave links in the C-band on a WDM network; the generated optical microwaves were distributed to their designated remote stations according to the channel wavelength. When the FU-OEO was used as the system LO, the phase noise of the optical microwaves was under −80 dBc/Hz at a 10 kHz offset from a 20 GHz carrier frequency. As a frequency up-converter, the FU-OEO simultaneously up-converted all optical data channels at a 1.25 Gbps data rate for optical microwaves in the 20 GHz band of an optical carrier suppression mode having almost 100% modulation depth. The overall system performance was verified by measuring the bit error rates (BER) of the data recovered from optical microwaves received through single-mode fibers. The measured BER indicated that the system can transmit over 50 km with a power penalty of less than 1 dB. This method can be useful for high-frequency applications where the generation and transmission of optical microwaves are greatly restricted by optical or electrical bandwidths.

This paper introduces the background and basic theory of flexible repeater technology, then analyses the basic working process and principle of flexible repeater on Wideband Gapfiller Satellite (WGS), and summarizes the key technologies during implementation. Meantime, for solving the large capacity and multi-beam connection problems in mobile satellite communication system, the flexible repeater provides the necessary basis theoretical and technical support. Finally, by comparing the tradition repeaters with flexible repeater, this paper points out the flexible repeater possesses the virtue of high power efficiency and high flexibility, and could realize flexible switching of the satellite signals and resources.

We show that the minimum EOP (eye-opening penalty) obtained by tunable dispersion compensation is a function of a figure of merit for a nonlinear process, I0Leff, where I0 is the optical intensity and Leff is the effective length of the interaction region. Using this rule, we do not need to conduct nonlinear simulations in all the cases of signal power and transmission length to obtain the signal distortion in dispersion-managed optical transmission. Instead, we need to conduct a simulation in only one case of a signal power and find the functional relation, and then we can obtain the values of the signal distortion in other cases using the discovered functional relation. This technique can reduce the number of nonlinear simulations to less than 10%.

This paper discusses nonlinear optical signal processing employed in optical packet switching systems. Nonlinear optical signal processing provides optical label (header) recognition, optical switching, wavelength conversion, and time buffering with typically higher capacity, lower latency, and lower power consumption than electronic counterparts. In order to provide diverse signal processing functions, large-scale integration of nonlinear optical signal processing devices is essential. We discuss possible future directions in optical packet switching involving nonlinear optical signal processing of optical packets with advanced data and label modulation formats.

A video signal through a high-density optical link has been demonstrated to show the reliability of optical link for highdata-rate transmission. To reduce optical point-to-point links, an electrical link has been utilized for control and clock signaling. The latency and flicker with background noise occurred during the transferring of data across the optical link due to electrical-to-optical with optical-to-electrical conversions. The proposed synchronization technology combined with a flicker and denoising algorithm has given good results and can be applied in high-definition serial data interface (HD-SDI), ultra-HD-SDI, and HD multimedia interface transmission system applications.

Orthogonal frequency division multiplexing (OFDM) is a suitable solution thanks to its many advantages known in wireless communications. On the other hand, optical communications is also used as a backbone to transmit and receive large data rates with economical and good performance. Recently, fiber optical communication and OFDM method have been combined to obtain both advantages in a communication link called Coherent Optical OFDM (CO-OFDM). In this study, Bit error rate (BER) versus distance variations are investigated for a constant signal to noise ratio in CO-OFDM systems. Results also show the performance of the CO-OFDM system at different data rates and distances for one RF carrier and one optical carrier. So far, the Telecommunication Standardization Sector standards have suggested 81 channels between 192.1 and 196.1 THz in C band. Extending the number of channels using 111 more channels between 185.9 and 191.4 THz in L band where optical amplifiers and laser sources are available, the total number of channels reaches up to 192. In this research, CO-OFDM technique is modeled and simulated designing a Monte Carlo simulation. Dense wavelength division multiplexing (DWDM) is the key factor to obtain 3 Tb/s (192*16 Gb/s) utilizing only one optical cable by covering whole C and L bands. To the best of our knowledge, this work shows the first BER versus Distance variations in a CO-OFDM communication link for 3 Tb/s.

A scheme that utilizes the 4-level pulse-amplitude-modulated (4PAM) signal as the re-modulated signal of colorless optical network units (ONUs) based on reflection semiconductor optical amplifiers (RSOAs) is proposed. The system with 10-Gb/s non-return-to-zero (NRZ) downstream and 5-Gb/s 4PAM upstream signals is theoretically analyzed and experimentally verified. Simulation and experimental results reveal that the 4PAM re-modulated signal yields better performance than the NRZ signal in the upstream. A receiver power penalty of 1.6 dB is also improved by the 4PAM signal at back-to-back (BtB) transmission, whereas another receiver power penalty of 1.5 dB improved after 30-km single mode fiber transmission, where 4PAM signals are used as upstream signal.

To support efficient delivery of packet and circuit services simultaneously in future optical networks, software will play more and more important roles, not only in control and management plane, but also in transport plane. This article discusses a new concept of cognitive optical networks utilizing intelligent software (e.g., digital signal processing in the optical transport plane and GMPLS in the optical control plane) as well as flexible optics (e.g., colorless, directionless, contentionless, gridless ROADM, and optical OFDM). The software-defined CON architecture with advanced capabilities such as quality of transmission awareness and client service awareness is capable of provisioning adaptive bandwidth services at wavelength and sub-wavelength levels, making future optical networks more cognitive and reconfigurable.