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.      

100-Gb/s Packet Signal Generation With Spectral Efficiency Larger Than 1 bit/Hz/s

We have experimentally demonstrated how to generate 100-Gb/s packet signals with spectral efficiency higher than 1bit/Hz/s for the first time. The optical packet with 3.125-Gb/s label and 100-Gb/s return-to-zero differential quadrature phase-shift-keying payload are generated by using optical carrier-suppression and separation and vestigial sideband filtering techniques. The performance of transmission and label erasure has also been evaluated.     

107-Gb/s Serial Optical Packet Switching With 1-bit/s/Hz Spectral Efficiency for 100-GbE Backplanes

We demonstrate 107-Gb/s optical packet switching using electronically multiplexed duobinary signals, fast tunable lasers, and a 40 times 40 arrayed waveguide grating router. With a spectral efficiency of 1 bit/s/Hz, the fabric scales to 4-Tb/s capacity and is suitable for 100-Gb Ethernet backplanes.     

50-Gb/s 4-b multiplexer/demultiplexer chip set using InP HEMTs

A 50-Gb/s 4:1 multiplexer (MUX) and 1:4 demultiplexer (DEMUX) chip set using InP high electron mobility transistors (HEMTs) is described. In order to achieve wide-range bit-rate operation from several to 50 Gb/s, timing design inside the ICs was precisely executed. The packaged MUX operated from 4 to 50Gb/s with >1-V/sub pp/ output amplitude, and the DEMUX exhibited >180/spl deg/ phase margin from 4 to 50 Gb/s for 2/sup 31/-1 pseudorandom bit sequence (PRBS). Furthermore, 50-Gb/s back-to-back error-free operation for 2/sup 31/-1 PRBS was confirmed with the packaged MUX and DEMUX.     

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.      

1500-km SSMF Transmission of Mixed 40-Gb/s CS-RZ Duobinary and 100-Gb/s CS-RZ DQPSK Signals

We demonstrated transmission of eight channelsof 200-GHz channel spacing and 100-Gb/s carrier-suppressed return-to-zero (CS-RZ) differential quadrature phase-shift keying (DQPSK) signals together with eight channels of 40-Gb/s CS-RZ duobinary (DRZ) signals also with 200-GHz channel spacing in order to improve the optical spectral efficiency of the wavelength-division-multiplexing system. Each DRZ channel is inserted in the middle of two adjacent CS-RZ DQPSK channels. A bit-error rate (BER) of less than 5E-4 is achieved for the 40-Gb/s DRZ channel after 1500-km SSMF transmission while a BER of 1E-3 is achieved for the 100-Gb/s CS-RZ DQPSK signals.      

42.8-Gb/s RZ-DQPSK Transmission With FBG-Based In-Line Dispersion Compensation

Phase ripple impairments induced through cascaded fiber Bragg gratings (FBGs) are discussed for 42.8-Gb/s transmission. We show the feasibility of transmission over 1140 km (12 times 95 km) using return-to-zero differential quadrature phase-shift keying modulation and FBG-only dispersion compensation. We further compare FBGs with dispersion-compensating fiber for dispersion compensation and analyze the influence of wavelength detuning.     

Stable 100-Gb/s POLMUX-DQPSK Transmission With Automatic Polarization Stabilization

The reliability of 100-Gb/s polarization-multiplexed return-to-zero differential quadrature phase-shift keying transmission is demonstrated exploiting direct detection and automatic polarization stabilization. We experimentally verified a 2-dB chromatic dispersion tolerance of 100 ps/nm. Long-term stability has also been assessed by sampling the bit-error rate every 3 min over a continuous period of 8 h. Measurements are performed both in back-to-back and after 8.8-km uncompensated standard single-mode fiber, in the presence of a polarization scrambler.      

8 bit 1.4 GS/s 模数转换器

超高速模数转换器(ADC)是软件无线电、高速数据采集和宽带数字化雷达的关键组成部分.附带校准技术的折叠内插ADC具有等同快闪(FLASH)ADC的高转换速度,是设计超高速ADC的最佳选择,但仍需综合考虑各项指标来时行校准方法设计及芯片架构优化.     

A 0.3-μm CMOS 8-Gb/s 4-PAM serial link transceiver

An 8-Gb/s 0.3-μm CMOS transceiver uses multilevel signaling (4-PAM) and transmit preshaping in combination with receive equalization to reduce intersymbol interference due to channel low-pass effects. High on-chip frequencies are avoided by multiplexing and demultiplexing the data directly at the pads. Timing recovery takes advantage of a novel frequency acquisition scheme and a linear phase-locked loop that achieves a loop bandwidth of 35 MHz, phase margin of 50°, and capture range of 20 MHz without a frequency acquisition aid. The transmitted 8 Gb/s data are successfully detected by the receiver after a 10-m coaxial cable. The 2×2 mm² chip consumes 1.1 W at 8 Gb/s with a 3-V supply     

Highly Spectrally Efficient DWDM Transmission at 7.0 b/s/Hz Using 8 65.1-Gb/s Coherent PDM-OFDM

In this paper, we discuss the realization of wavelength-division multiplexing (WDM) transmission at high spectral efficiency. For this experiment, coherent polarization-division multiplexing--orthogonal frequency-division multiplexing (PDM-OFDM) is used as a modulation format. PDM-OFDM uses training symbols for channel estimation. This makes OFDM easily scalable to higher level modulation formats as channel estimation is realized with training symbols that are independent of the constellation size. Furthermore, because of its well-defined spectrum OFDM requires only a small guard band between WDM channels. The dependence of the number of OFDM subcarriers is investigated with respect to the interchannel linear crosstalk. At a constant data rate the number of OFDM subcarriers is estimated to achieve lower linear crosstalk in order to achieve higher spectral efficiency. We then experimentally demonstrate dense WDM (DWDM) transmission with 7.0-b/s/Hz net spectral efficiency using 8 $,times,$65.1-Gb/s coherent PDM-OFDM signals with 8-GHz WDM channel spacing utilizing 32-quadrature-amplitude-modulation subcarrier modulation. Successful transmission is achieved over 240 km standard single-mode fiber (SSMF) spans with hybrid erbium-doped fiber amplifiers/Raman amplification.      

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.      

High-Spectral-Efficiency 114-Gb/s Transmission Using PolMux-RZ-8PSK Modulation Format and Single-Ended Digital Coherent Detection Technique

Employing spectrally efficient PolMux-RZ-8PSK modulation format and single-ended digital coherent detection technique, we demonstrate 8$,times,$114-Gb/s DWDM transmission over 640 km of SSMF on a 25-GHz grid with record spectral efficiency of 4.2 bit/s/Hz, utilizing no optical dispersion compensation or Raman amplification. We show that the distortion caused by the direct square-law detection of the signal component with single-ended photo detection can be effectively mitigated by a novel DSP algorithm.      

Transmission of 160-Gb/s Modified Manchester modulation over WDM system

The paper examines the performance of Modified Manchester (MM) modulation scheme over wavelength division multiplexing (WDM) in high-speed optical communication links. The MM as a new modulation technique has a narrow spectral width compared to conventional Manchester coding, which allows its implementation in WDM systems beneficial. In this study, the performance characteristics of MM and conventional Manchester modulation formats are assessed in WDM system at 10 Gb/s bitrate for each channel, for the least allowable channel spacing as well as tolerance to chromatic dispersion (CD). It is revealed from the results of simulation that MM performs meaningfully well in comparison with conventional Manchester in terms of tolerance against narrow optical filtering, spectral efficiency, which is improved by 32% and CD tolerance, which is improved by +100 ps/nm. Sixteen wavelength channels (16 × 10 Gb/s) are modulated to provide 160 Gb/s data capacity, which was transmitted successfully over 224 km standard single mode fibre (SSMF) using MM while the conventional Manchester only covered about 157 km.     

Coherent Optical 25.8-Gb/s OFDM Transmission Over 4160-km SSMF

We discuss coherent optical orthogonal frequency division multiplexing (CO-OFDM) as a suitable modulation technique for long-haul transmission systems. Several design and implementation aspects of a CO-OFDM system are reviewed, but we especially focus on phase noise compensation. As conventional CO-OFDM transmission systems are very sensitive to laser phase noise a novel method to compensate for phase noise is introduced. With the help of this phase noise compensation method we show continuously detectable OFDM transmission at 25.8 Gb/s data rate (20 Gb/s after coding) over 4160-km SSMF without dispersion compensation.     

A 4-Gb/s CMOS clock and data recovery circuit using 1/8-rate clock technique

A 4-Gb/s clock and data recovery (CDR) circuit is realized in a 0.25-/spl mu/m standard CMOS technology. The CDR circuit exploits 1/8-rate clock technique to facilitate the design of a voltage-controlled oscillator (VCO) and to eliminate the need of 1:4 demultiplexer, thereby achieving low power consumption. The VCO incorporates the ring oscillator configuration with active inductor loads, generating four half-quadrature clocks. The VCO control line comprises both a programmable 6-bit digital coarse control and a folded differential fine control through a charge-pump and a low pass filter. Duty-cycle correction of clock signals is obtained by exploiting a high common-mode rejection ratio differential amplifier at the ring oscillator output. A 1/8-rate linear phase detector accomplishes the phase error detection with no systematic phase offset and inherently performs the 1:4 demultiplexing. Test chips demonstrate the jitter of the recovered clock to be 5.2 ps rms and 47 ps pk-pk for 2/sup 31/-1 pseudorandom bit sequence (PRBS) input data. The phase noise is measured to be -112 dBc/Hz at 1-MHz offset. The measured bit error rate is less than 10/sup -6/ for 2/sup 31/-1 PRBS. The chip excluding output buffers dissipates 70 mW from a single 2.5-V supply.     

Comparison of 112-Gb/s PM-RZ-DQPSK and PM-RZ-D8PSK in Terms of OSNR Requirement and Transmission Impairments

We have, for the first time, experimentally investigated 112-Gb/s polarization-multiplexed return-to-zero differential 8-ary phase-shift keying (PM-RZ-D8PSK) with differential detection in terms of optical signal-to-noise ratio requirement, group velocity dispersion (GVD), and differential group delay (DGD) tolerances, together with a direct comparison with PM-RZ differential quadrature phase-shift keying at equivalent bit rate. The results indicate higher tolerances with respect to GVD and DGD but lower receiver sensitivity in the case of PM-RZ-D8PSK.      

An 8-b ADC with over-Nyquist input at 300-Ms/s conversion rate

An 8-b flash analog-digital (A/D) converter (ADC) LSI for high-speed data acquisition systems such as digital oscilloscopes and wave digitizers is described. This converter can convert analog input signals over the Nyquist frequency (up to 200 MHz) at a conversion rate of 300 megasamples per second (Ms/s) without glitch errors. In addition, it can be operated at up to 440 Ms/s when input frequency is as low as 100 kHz. This ADC is fabricated by a 2.5-μm, 10-GHz f_T , Si bipolar technology called the advanced sidewall base contact structure (advanced SICOS) technology. For high-performance glitch error suppression, an inhibitory circuit and a comparator design with an inner clock buffer are developed. Both techniques require few hardware additions     

Performance Comparison of Duobinary Formats for 40-Gb/s and Mixed 10/40-Gb/s Long-Haul WDM Transmission on SSMF and LEAF Fibers

Duobinary formats are today considered as being one of the most promising cost-effective solutions for the deployment of 40-Gb/s technology on existing 10-Gb/s WDM long-haul transmission infrastructures. Various methods for generating duobinary formats have been developed in the past few years but to our knowledge their respective performances for 40-Gb/s WDM transmission have never been really compared. In this paper, we made an extensive numerical evaluation of the robustness of these different types of duobinary transmitter to accumulation of ASE noise, chromatic dispersion, PMD but also to single-channel and WDM 40-Gb/s transmission impairments on standard single-mode fiber. A numerical evaluation of the ability of duobinary format for mixed 10/40-Gb/s WDM long-haul transmission with 50-GHz channel spacing is also led, on both standard single-mode and LEAF fibers, and compared to DQPSK format. In order to clearly identify the limiting transmission effects on each of these two fiber types, the assessment of the performance of a 50-GHz spaced WDM 40-Gb/s long-haul transmission using either duobinary or DQPSK channels only is implemented at last.      

A 690-mW 1-Gb/s 1024-b, rate-1/2 low-density parity-check codedecoder

A 1024-b, rate-1/2, soft decision low-density parity-check (LDPC) code decoder has been implemented that matches the coding gain of equivalent turbo codes. The decoder features a parallel architecture that supports a maximum throughput of 1 Gb/s while performing 64 decoder iterations. The parallel architecture enables rapid convergence in the decoding algorithm to be translated into low decoder switching activity resulting in a power dissipation of only 690 mW from a 1.5-V supply