WDM PON using 10-Gb/s DPSK downstream and re-modulated 10-Gb/s OOK upstream based on SOA

A signal remodulation scheme of 10-Gb/s differential phase-shift keying(DPSK) downstream and 10-Gb/s on-off keying(OOK) upstream using a semiconductor optical amplifier(SOA) and a Mach-Zehnder intensity modulator(MZ-IM) at the optical networking unit(ONU) side for wavelength division multiplexed passive optical network(WDM PON) is proposed.Simulation results indicate that error-free operation can be achieved in a 20-km transmission,and the receiver sensitivity of return-to-zero differential phase-shift keying(RZ-DPSK) is higher than nonreturn-to-zero differential phase-shift keying(NRZ-DPSK) in the proposed scheme.     

Measured Noise Performance for Heterodyne Detection of 10-Gb/s OOK and DPSK

Heterodyne detection of 10-Gb/s nonreturn-to-zero (NRZ) on-off keying and NRZ differential phase-shift keying is demonstrated. The noise performance of the heterodyne receiver with and without the use of an optical preamplifier is experimentally investigated     

Low insertion loss and low dispersion penalty InGaAsP quantum-well high-speed electroabsorption modulator for 40-Gb/s very-short-reach, long-reach, and long-haul applications

We present a metal-organic-chemical-vapor-deposition-grown low-optical-insertion-loss InGaAsP/InP multiple-quantum-well electroabsorption modulator (EAM), suitable for both nonreturn-to-zero (NRZ) and return-to-zero (RZ) applications. The EAM exhibits a dynamic (RF) extinction ratio of 11.5 dB at 1550 nm for 3 Vp-p drive under 40-Gb/s modulation. The optical insertion loss of the modulator in the on-state is -5.2 dB at 1550 nm. In addition, the EAM also exhibits a 3-dB small-signal response (S21) of greater than 38 GHz, allowing it to be used in both 40-Gb/s NRZ and 10-Gb/s RZ applications. The dispersion penalty at 40 Gb/s is measured to be 1.2 dB over /spl plusmn/40 ps/nm of chromatic dispersion. Finally, we demonstrate 40-Gb/s transmission performance over 85 km and 700 km.     

40-Gb/s tandem electroabsorption modulator

In this letter, we have developed a tandem electroabsorption modulator with an integrated semiconductor optical amplifier that is capable of both nonreturn-to-zero and return-to-zero (RZ) data transmission at 40 Gb/s. The tandem modulator consists of a broad-band data encoder and a narrow-band pulse carver. The pulse carver is able to produce 5-ps pulses with more than 20 dB of extinction. The on-chip semiconductor optical amplifier provides up to 8.5 dB of fiber-to-fiber gain and enables the modulator to be operated with zero insertion loss. Devices have been realized with greater than 40-GHz bandwidth, and 13-dB dynamic extinction for a 2.5-V swing. For optimized designs bandwidths of nearly 60 GHz: have been realized. Using these devices penalty free RZ data transmission over a 100-kin dispersion compensated fiber link has been demonstrated with a received power sensitivity of -29 dBm     

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.      

Semiconductor light sources for 40-Gb/s transmission systems

The status and prospects of semiconductor light sources for 40-Gb/s transmission systems are reviewed in regard to the following three topics: direct modulation, external modulation, and pulse sources for return-to-zero format. Included are discussions on direct modulation of a 1.3-/spl mu/m distributed feedback laser for 40-Gb/s very-short-reach optical links, progress made in developing external modulators based on electroabsorption of multiple quantum wells, and mode-locked lasers for carrier-suppressed return-to-zero modulation format.     

40-Gb/s ICs for future lightwave communications systems

This paper describes the device, circuit design, and packaging technologies applicable to 40-Gb/s-class future lightwave communications systems. A 0.1-μm gate InAlAs-InGaAs high electron mobility transistors (HEMTs) with InP recess etch stopper was adopted mainly for IC fabrication. Fabricated ICs demonstrate excellent data-multiplexing, demultiplexing, and amplifying operation at 10 Gb/s     

Low-Voltage Topologies for 40-Gb/s Circuits in Nanoscale CMOS

This paper presents low-voltage circuit topologies for 40-Gb/s communications in 90-nm and 65-nm CMOS. A retiming flip-flop implemented in two different 90-nm CMOS technologies employs a MOS-CML Master-Slave latch topology with only two vertically stacked transistors. Operation at 40 Gb/s is achieved by a combination of low and high-V_T MOSFETs in the latch. Full-rate retiming with jitter reduction is demonstrated up to 40 Gb/s. Low-power broadband amplifiers based on resistor-inductor transimpedance feedback are realized in 90-nm and 65-nm CMOS to investigate the portability of high-speed building blocks between technology nodes. Experiments show that the transimpedance amplifier based on the CMOS inverter can reach 40-Gb/s operation with a record power consumption of 0.15 mW/Gb/s. A comparison between CMOS technologies underlines the importance of General Purpose rather than Low Power processes for high-speed digital design.     

Self-Coherent Decision-Feedback-Directed 40-Gb/s DQPSK Receiver

A novel 40-Gb/s differential quadrature phase-shift keying receiver is theoretically proposed, improving direct detection by 4.2 dB for self-phase-modulation-limited single-channel transmission, approaching ideal coherent homodyne performance using a recirculating delay line interferometric integrated-optical circuit front-end combining decision feedback and nonlinear phase-noise compensation     

Rayleigh Backscattering Noise-Eliminated 115-km Long-Reach Bidirectional Centralized WDM-PON With 10-Gb/s DPSK Downstream and Remodulated 2.5-Gb/s OCS-SCM Upstream Signal

We propose a novel scheme of Rayleigh backscattering noise-eliminated, long-reach, single-fiber, full-duplex, centralized wavelength-division multiplexed passive optical network with differential quadrature phase-shift keying (DPSK) downstream and remodulated upstream using an optical carrier-suppressed subcarrier-modulation (OCS-SCM) technique and optical interleaver. The error-free transmissions of 10-Gb/s downstream and 2.5-Gb/s upstream signals are experimentally demonstrated over 115-km single-fiber bidirectional SMF-28 with less than 0.5 and 1.9 dB power penalties, respectively.      

Clock and data recovery IC for 40-Gb/s fiber-optic receiver

The integrated clock and data recovery (CDR) circuit is a key element for broad-band optical communication systems at 40 Gb/s. We report a 40-Gb/s CDR fabricated in indium-phosphide heterojunction bipolar transistor (InP HBT) technology using a robust architecture of a phase-locked loop (PLL) with a digital early-late phase detector. The faster InP HBT technology allows the digital phase detector to operate at the full data rate of 40 Gb/s. This, in turn, reduces the circuit complexity (transistor count) and the voltage-controlled oscillator (VCO) requirements. The IC includes an on-chip LC VCO, on-chip clock dividers to drive an external demultiplexer, and low-frequency PLL control loop and on-chip limiting amplifier buffers for the data and clock I/O. To our knowledge, this is the first demonstration of a mixed-signal IC operating at the clock rate of 40 GHz. We also describe the chip architecture and measurement results.     

40-Gb/s high-power modulator driver IC for lightwave communicationsystems

A monolithic integrated modulator driver with a data decision function for high-speed optical fiber links is presented. The integrated circuit (IC) was manufactured in a 0.2-μm gate length AlGaAs/InGaAs high electron mobility transistor technology with an f_T of 68 GHz. The modulator driver IC features differential configuration and operates up to 40 Gb/s with a clock phase margin of 210° and an output voltage swing of 2.9 V_p-p at each output. The maximum slew rate of the output signal is 200 mV/ps. The power dissipation of the circuit is 1.6 W using a single supply voltage of -5 V     

Prechirp in NRZ-based 40-Gb/s single-channel and WDM transmissionsystems

We investigate the impact of the prechirp on nonreturn-to-zero (NRZ)-based single-channel and 40-Gb/s/ch wavelength-division-multiplexing systems over standard single-mode fibers by means of numerical simulations. It was shown that prechirping of NRZ pulses improve the total transmission length and make the NRZ pulses more robust to Kerr-nonlinearities     

基于锗硅工艺的40-Gb/s分接器

采用0.35μmSiGeBiCMOS工艺设计了一个1∶2分接器,核心电路单元采用经过改进的电路结构实现。由于传统的发射极耦合逻辑结构(ECL)电路的工作速度不能达到要求,对此加以了改进,在发射极耦合逻辑结构中增加一级射极跟随器,形成发射极-发射极耦合逻辑(E2CL)结构,从而提高电路的工作速度。测试结果显示,所设计分接器的工作速度可以达到40Gb/s。整个电路采用单电源5V供电,功耗为510mW。     

High-Performance and Low-Cost 40-Gb/s CWDM Optical Modules

High-performance and low-cost 40-Gb/s optical modules using four different wavelength uncooled 10-Gb/s distributed-feedback (DFB) lasers are proposed and demonstrated. The 40-Gb/s optical module was integrated with coarse wavelength division multiplexing (CWDM) thin-film filters which enabled four 10-Gb/s transmission channels output through a single fiber. The 10-Gb/s DFB laser was packaged by commercialized low-cost coaxial TO-Can technology. The results of the 40-Gb/s optical module showed that the output optical power was above ${-}1$ dBm per channel and the system power budget was 12 dB. The transmission distance with a single-mode fiber reached more than 30 km at a bit-error-rate of $10^{{-}9}$. Compared with conventional 40-Gb/s optical modules, the module is easy to fabricate and is low cost. This proposed high-performance 40-Gb/s CWDM optical module demonstrates not only the feasibility of a 30 km transmission, but also shows the low-cost possibility of ensuring the application of WDM-passive optical network fiber-to-the-home systems.      

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.      

Nonlinearity Limitations When Mixing 40-Gb/s Coherent PDM-QPSK Channels With Preexisting 10-Gb/s NRZ Channels

We investigate the penalties onto a 40-Gb/s polarization-division-multiplexing (PDM)-quadrature phase-shift keying caused by PDM, wavelength-division multiplexing and 10-Gb/s nonreturn-to-zero neighbor channels. Besides, we optimize the carrier phase estimation process and introduce bandgaps in the multiplex in order to contain limitations caused by cross nonlinear effects.     

Residual Chromatic-Dispersion Monitoring and Dynamic Compensation in 40-Gb/s Systems

A dynamic chromatic-dispersion-compensation system is implemented with a residual chromatic-dispersion monitoring module based on self-frequency shift effects in a semiconductor optical amplifier. Experimental results show that the compensation range of the system is 100 ps/nm and the residual chromatic dispersion of the transmission link is less than 5 ps/nm.     

Ghost-pulse generation suppression in phase-modulated 40-Gb/s RZ transmission

40-Gb/s return-to-zero (RZ) transmission in strong dispersion maps is limited by single-channel four-wave mixing. Appropriate phase modulation of the signal suppresses generation of the ghost pulses. Duobinary and modified duobinary encoding produce cancellation of nonlinear interaction while carrier-suppressed RZ generates perturbations that add up coherently.