Transmission of 32-Tb/s Capacity Over 580 km Using RZ-Shaped PDM-8QAM Modulation Format and Cascaded Multimodulus Blind Equalization Algorithm

In this paper, we propose a novel synthesizing method for high-speed 8-ary quadratic-amplitude modulation (QAM) optical signal generation using commercial optical modulators with binary electrical driving signals. Using this method, we successfully generated 114-Gb/s pulse-duration modulation (PDM)-8QAM optical signals. Intradyne detection of PDM-8QAM optical signals with robust blind polarization demultiplexing has been demonstrated by using a new cascaded multimodulus equalization algorithm. With return-to-zero-shaped PDM-8QAM modulation and the proposed blind polarization demultiplexing algorithm, we demonstrate transmission of a record 32-Tb/s fiber capacity (320$,times,$114 Gb/s) over 580 km of ultralow-loss single-mode fiber-28 fiber by utilizing ${rm C}+{rm L}$-band erbium-doped fiber-amplifier-only optical amplification and single-ended coherent detection technique at an information spectral efficiency of 4.0 bit/s$cdot$Hz.      

256-QAM (64 Gb/s) Coherent Optical Transmission Over 160 km With an Optical Bandwidth of 5.4 GHz

We report a polarization-multiplexed (Pol-Mux) 4-Gsymbol/s 256 quadrature amplitude modulation (QAM) coherent optical transmission over 160 km. A 64-Gb/s data signal was successfully transmitted with an optical bandwidth of 5.4 GHz. We also describe a Pol-Mux, 10-Gsymbol/s, 128- and 64-QAM (140 and 120 Gb/s) transmission over 150 km.      

121.9-Gb/s PDM-OFDM Transmission With 2-b/s/Hz Spectral Efficiency Over 1000 km of SSMF

We discuss optical multi-band orthogonal frequency division multiplexing (OFDM) and show that by using multiple parallel OFDM bands, the required bandwidth of the digital-to-analogue/ analogue-to-digital converters and the required cyclic prefix can significantly be reduced. With the help of four OFDM bands and polarization division multiplexing (PDM) we report continuously detectable transmission of 10$,times,$ 121.9-Gb/s (112.6-Gb/s without OFDM overhead) at 50-GHz channel spacing over 1,000-km standard single mode fiber (SSMF) without any inline dispersion compensation. In this experiment 8 QAM subcarrier modulation is used which confines the spectrum of the 121.9 Gb/s PDM-OFDM signal within a 22.8 GHz optical bandwidth. Moreover, we propose a digital signal processing method to reduce the matching requirements for the wideband transmitter IQ mixer structures required for PDM-OFDM.      

Square Geometrical Shaping 128QAM Based Time Domain Hybrid Modulation in Visible Light Communication System

We proposed two kinds of visible light communication(VLC)systems which respectively based on 64QAM/square geometrical shaping(SGS)128QAM time domain hybrid modulation scheme(SGSHY)and 64QAM/128QAM time domain hybrid modulation scheme(REGHY).These two systems can operate around specific forward error correction(FEC)threshold and maximize the achievable information rate(AIR)of the system.The principles of SGSHY and REGHY are proposed in detail,which has very low computation complexity compared with probabilistic shaping.The SGSHY outperforms REGHY at high peak to peak voltage(Vpp).Experimental results show that at high Vpp like 1.4V,which means the system is suffering from high nonlinear distortion,the AIR of SGSHY outperforms that of REGHY by 0.12Gb/s at the 2×10-2 FEC threshold.The AIR of the REGHY is at most 0.36Gb/s higher than that of 64QAM at 0.8V Vpp and 7%FEC threshold,while the(achievable information rate)AIR of SGSHY is at most 0.40Gb/s higher than that of 64QAM at 1.4V Vpp and 20%FEC threshold.     

47.4 Gb/s Transmission Over 100 m Graded-Index Plastic Optical Fiber Based on Rate-Adaptive Discrete Multitone Modulation

We experimentally demonstrate a bit-rate of 47.4 Gb/s over 100 m of perfluorinated multimode graded-index plastic optical fiber (GI-POF) by exploiting discrete multitone (DMT) modulation with rate-adaptive bit-loading. The maximum achieved aggregate bit rate is 51.8 Gb/s including DMT transmission overhead (cyclic prefix and preambles) and the standard of 7% of forward-error-correction (FEC) overhead. This is achieved over an intensity-modulated direct-detection (IM-DD) link using a directly-modulated DFB laser (1300-nm) and a multimode fiber-coupled photodetector with a large diameter of 25-$mu$m. The bandwidth requirement is only 12 GHz due to the use of spectral-efficient modulation formats of up to 64-QAM.      

不同调制格式对400 Gb/s通信系统传输容量和距离的影响

单载波400 Gb/s传输是下一代通信系统的主要应用速率,为提高此速率通信在实际工程应用中的传输效率,理论分析了高速通信系统中不同调制方式与传输谱宽的关系,基于16阶正交幅度调制(16QAM)、16QAM/32QAM混传、32QAM、32QAM/64QAM混传和64QAM 5种不同调制格式,对400 Gb/s传输系统的...     

160 Gb/s Time-Domain Channel Extraction/Insertion and All-Optical Logic Operations Exploiting a Single PPLN Waveguide

160 Gb/s all-optical signal processing is demonstrated exploiting pump depletion in addition to sum and difference frequency generation (SFG/DFG) in a single periodically poled lithium-niobate (PPLN) waveguide. 160 Gb/s time-domain extraction and insertion operations of channels are obtained in an optical time division multiplexing (OTDM) system. Moreover, 160 Gb/s digital operations including half-adder, half-subtracter and and/or/xor functions are carried out. The use of pump depletion effect allows to process ultrafast signals due to its high efficiency and ultrafast dynamics. 160 Gb/s bit error rate (BER) measurements confirm the effectiveness of all presented functionalities.      

1-Gsymbol/s 64-QAM Coherent Optical Transmission Over 150 km

Quadrature amplitude modulation (QAM) is an excellent modulation format for realizing optical communication systems with a high spectral efficiency of much greater than 1bit/s/Hz. We describe QAM coherent optical communication that we achieved by using heterodyne detection with a frequency-stabilized fiber laser and an optical phase-locked loop (OPLL) technique. The phase error variance of the intermediate frequency signal of the OPLL was 6.1times10^-3 rad. A 1-Gsymbol/s 64-QAM coherent signal was successfully transmitted over 150km     

High Modulation Efficiency Gigabit/s Modulation of Twin-Contact High-Brightness Tapered DBR Laser

We report a compact single-chip optical transmitter with 0.4-W output optical modulation amplitude at 1 Gb/s using a twin-contact directly modulated laser with an applied ${sim}$ 100-mA current swing. Bit-error-ratio measurements confirm high signal quality for optical wireless communications.      

Burst-Mode Electronic Equalization for 10-Gb/s Passive Optical Networks

Using computer simulations, it is shown how burst-mode electronic equalization in the optical line termination of a passive optical network (PON) allows 10 Gb/s in the upstream direction with directly modulated distributed-feedback lasers. This allows achieving 10 Gb/s using cost-effective components at the optical network unit. Fast convergence of the equalizer coefficients is achieved during the preamble of each burst using the recursive least squares algorithm instead of the least mean squares algorithm. With a nine-tap feed-forward equalizer, two-tap decision feedback equalizer, a physical reach of 38 km and a splitting factor of 32 can be achieved in the 1.5-$mu$m window, exceeding requirements for deployed PONs.      

Investigation of Transparency of FWM in SOA to Advanced Modulation Formats Involving Intensity, Phase, and Polarization Multiplexing

We experimentally investigate the real transparency of four-wave mixing (FWM) in semiconductor optical amplifiers to modulation formats involving intensity, phase, and polarization multiplexing. We exploit two different FWM polarization-independent schemes (that make use of two pumps) to wavelength-convert 40 Gb/s single-polarization and 80 Gb/s polarization-multiplexed signals in case of both nonreturn-to-zero ${ON}$ –${OFF}$ keying (NRZ-OOK) and NRZ differential phase-shift keying modulation formats. We found that, although FWM conversion is transparent to modulation formats employing phase and intensity, polarization-multiplexed signals pose serious limitations to all-optical processing transparency.      

Experimental Demonstration and Numerical Simulation of 107-Gb/s High Spectral Efficiency Coherent Optical OFDM

Orthogonal frequency-division multiplexing (OFDM) is a multicarrier modulation format in which the data are transmitted with a set of orthogonal subcarriers. Recently, this modulation format has been actively explored in the field of optical communications to take advantages of its high spectral efficiency and resilience to chromatic and polarization dispersion. However, to realize the optical OFDM at 100 Gb/s and beyond requires extremely high electronic bandwidth for the electronic signal processing elements. In this paper, we investigate orthogonal-band-multiplexed OFDM (OBM-OFDM) as a suitable modulation and multiplexing scheme for achieving bandwidth scalable and spectral efficient long-haul transmission systems. The OBM-OFDM signal can be implemented in either RF domain, or optical domain, or a combination of both domains. Using the scheme of OBM-OFDM, we show the successful transmission of 107 Gb/s data rate over 1000-km standard single-mode fiber (SSMF) without optical dispersion compensation and without Raman amplification. The demonstrated OBM-OFDM system is realized in optical domain which employs 2 $times$ 2 MIMO-OFDM signal processing and achieves high optical spectral efficiency of 3.3 bit/s/Hz using 4-QAM encoding. Additionally, we perform numerical simulation of 107-Gb/s CO-OFDM transmission for both single-channel and wavelength-division-multiplexed (WDM) systems. We find that the $Q$ -factor of OBM-OFDM measured using uniform filling of OFDM subbands is in fact more conservative, in particular, is 1.2 dB and 0.4 dB lower than using random filling for single-channel and WDM systems, respectively.      

60-GHz System-on-Packaging Transmitter for Radio-Over-Fiber Applications

Using ultra-high-speed electroabsorption modulator (EAM) devices for RF/optic conversion, we fabricated system-on-packaging (SOP) transmitter (Tx) modules and characterized their performance in 60-GHz RF/radio-over-fiber (ROF) applications. Both an EAM and low-noise amplifiers (LNAs) were co-packaged with internal bias circuits into a butterfly-type metal housing. At the EAM temperature, $T {sim} {hbox{25}}~^{circ}$ C and the EAM reverse bias, $V_{R} {sim} $1.6 V was the largest RF gain obtained that was very susceptible to the change of $T$ . The impedance matching in the 60-GHz band was accomplished with both a microstrip-line bandpass filter and a 500- $Omega$ shunt resistor, which defined the 2-GHz passband of the SOP transmitter. In 60-GHz two-tone experiments, we observed that the spurious free dynamic range of an SOP module with two LNAs was 78 dB $cdot$ Hz $^{2/3}$ while that of the narrowband EAM module showed 82 dB $cdot$ Hz$^{2/3}$. In contrast, the noise figure exhibited a large reduction of up to 30 dB for the SOP module compared with the narrowband EAM module. Using the SOP Tx module, we achieved successful transmission of commercial high-definition digital CATV signals in 64-quadrature amplitude modulation (QAM) format through the 60-GHz RF/ROF link. The total throughput of the link was estimated to be 6.5 Gb/s.      

10-Gb/s Operation of RSOA for WDM PON

We report on the 10-Gb/s operation of the reflective semiconductor optical amplifier (RSOA) for the next-generation wavelength-division-multiplexed passive optical network (WDM PON). The bandwidth of the RSOA used in this experiment is merely 2.2 GHz. Nevertheless, a clear eye opening is obtained at 10 Gb/s by using the electronic equalizer processed offline. We investigate the impacts of the network's operating conditions (such as the injection power to the RSOA and the fiber length) on the performances of these equalizers. The results show that the RSOA-based WDM PON is operable at 10 Gb/s and the maximum reach can be extended to ${>}$ 20 km with the help of the forward error correction codes.      

1.28-Tb/s (32 $times$ 40 Gb/s) Free-Space Optical WDM Transmission System

We successfully transmitted a 1.28-Tb/s (32 $times$ 40 Gb/s) wavelength-division-multiplexed (WDM) signal over a free-space optic (FSO) link, for the first time. We used a novel pair of FSO terminals, transparently connected to optical fibers, to transmit/receive the WDM channels over a double-pass FSO path between two buildings (2 $times$ 210 m). Limited penalty on all 40-Gb/s channels and high stability was observed. Furthermore, long-term measurements of the system performance indicate a high improvement in reliability, which makes it a promising alternative for future deployment.      

Jitter Challenges and Reduction Techniques at 10 Gb/s and Beyond

The bandwidths of high-speed input/output (I/O) links keep increasing to meet the ever-growing demands for high-speed communications. The data rates for the leading edge high-speed I/O standards have already increased to around 10 Gb/s, including 10 GB Ethernet (GBE, 10 Gb/s, or 4 $,times,$10.3125 Gb/s, and 10$,times,$10.3125 Gb/s for Ethernet 40 G/100 G), 8$,times$ fibre channel (8.5 Gb/s), and PCI Express Gen 3 (at 8 Gb/s). At those data rates, the total available timing budget become less, data-dependent jitter gets severe, and jitter amplification becomes significant. This paper focuses on these jitter challenges and associated mitigation/reduction technologies, including jitter tracking via clock recovery, eye-opening via equalizations, and DCD cancellation via delay elements to avoid jitter amplification.      

System Performance of High-Order Optical DPSK and Star QAM Modulation for Direct Detection Analyzed by Semi-Analytical BER Estimation

Recently, higher order modulation formats are intensively investigated to further increase spectral efficiency for building next generation optical transport networks. Direct detection receivers are capable of detecting arbitrary modulation formats with differentially encoded phases such as differentially phase shift keying (DPSK) and star shaped quadrature amplitude modulation (Star QAM) formats. In an earlier publication of the authors (M. Seimetz , “Optical systems with high-order DPSK and star QAM modulation based on interferometric direct detection,” J. Lightw. Technol. , vol. 25, no. 6, pp. 1515–1530, Jun. 2007) a system analysis was performed where performance was mainly characterized by eye opening penalties. Here, these investigations are extended. A tool for semi-analytical BER estimation is developed allowing to calculate the BER down to small values such as $10^{-9}$ for a wide range of modulation formats, as well as for different receiver structures. Using this module, the back-to-back OSNR requirements are calculated. CD and SPM tolerances are characterized by optical signal-to-noise ratio (OSNR) penalties at ${hbox {BER}} = 10^{-9}$ . As far as the authors know, this is the first analysis of the transmission characteristics of optical 16DPSK and Star 16QAM based on the BER. Moreover, further novel aspects such as optimization of the optical and electrical receiver filter bandwidths are investigated.      

Multidimensional LDPC-Coded Modulation for Beyond 400 Gb/s per Wavelength Transmission

In this letter, we propose a multidimensional low-density parity-check-coded modulation scheme suitable for use in up to 400 Gb/s per wavelength transmission, using currently available commercial components operating at 40 gigasymbols/s. We show that we can achieve multiples of the current transmission speed with negligible penalty. At the same time, using this scheme, the transmission and signal processing are done at 40 gigasymbols/s, where dealing with all the nonlinear effects is more convenient and the polarization-mode dispersion is more manageable. In addition, we show that using the proposed technique, we can achieve an improvement ranging from 3 dB over 8-quadrature-amplitude modulation (QAM) to 14 dB over 256-QAM, and an improvement of up to 9.75 dB over the 256-3D-constellation at bit-error ratio (BER) of $10^{- 9}$. We also show that we can reach the 400-Gb/s aggregate rate with a coding gain of 10.75 dB at BER of $10^{- 12}$.      

Polymer-Waveguide-Based Board-Level Optical Interconnect Technology for Datacom Applications

On the basis of a realized 12$,times,$ 10 Gb/s card-to-card optical link demonstrator, the capabilities of a polymer-waveguide-based board-level optical interconnect technology are presented. The conception and realization of the modular building blocks required for this board-level optical interconnect technology are described in detail. In particular, we report on the fabrication and characterization of board-integrated optical low-loss polymer waveguides that are compatible with printed circuit board (PCB) manufacturing processes. We also explain our fully passive alignment technique, superseding time-consuming active positioning of components and connectors. To realize optical transceiver modules comprising vertical cavity surface emitting laser (VCSEL) arrays with laser drivers and photodetector arrays with transimpedance amplifiers (TIAs), a mass-production concept based on wafer-level processing has been elaborated and successfully implemented.      

640 Gbit/s (64-Wavelength $,times,$10 Gbit/s) Data-Rate Wide-Colored NRZ-DPSK Optical Packet Switching and Buffering Demonstration

We demonstrated optical packet switching and buffering operation of a DWDM/NRZ-DPSK optical packet, whose payload-data-rate is 640 Gbit/s (64-wavelength$,times,$10 Gbit/s), for transparent optical packet switch systems for the first time. Error-free (bit-error-rate ${≪}10^{- 9}$) operation including 200-Gchip/s PSK optical label processing was achieved for all 64-wavelength-channel 10 Gbit/s DPSK packet-payloads. In addition, the higher tolerance of DPSK format for packet power fluctuation compared with OOK one was verified in an optical packet switch system.