400 Mbit/s optical heterodyne DPSK system experiment with inline1.5 μm amplifiers

Reports a 400 Mbit/s differential phase shift keying (DPSK) heterodyne optical transmission system experiment using two inline packaged resonant type amplifiers. The optical amplifier gave a 14.5 dB net gain from fibre to fibre at λ=1.488 μm with no significant system penalty     

1.4 Gbit/s optical DPSK heterodyne transmission system experiment

The authors report the performance of a 1.4 Gbit/s differential phase shift keying (DPSK) coherent fibre system experiment using a balanced receiver. They show that the detection sensitivity as a function of local oscillator power follows the same functional dependence as the theoretical prediction     

100-Mbit/s semiduplex optical fiber transmission experiment using GaAs/GaAlAs laser transceivers

Semiduplex, high-data-rate transmission over a single optical fiber using GaAs/GaAlAs channeled substrate planar (CSP) structure lasers both as light source and photodetector has been demonstrated. The responsivity in the receiving mode at the operating wavelength (830 nm) was 0.15 A/W. This device is suitable for semiduplex transmission, since the emissive spot and the photosensitive area of the laser coincide. The impulse response was measured to be 2.5 ns full width at half maximum (FWHM) at zero bias voltage. A 500-m single-mode fiber was used, and by using microlenses the input coupling loss was reduced to less than 4.5 dB. Measurements at a data rate of 100 Mbit/s return to zero (RZ) shows an optical power margin of 14 dB for a bit error rate (BER) of 10^-9. Using lasers instead of LED's as transceivers would improve the transmission capability and the system margin of a semiduplex communication link.     

A 50-Mbit/s CMOS monolithic optical receiver

A general-purpose CMOS optical receiver that operates at data rates from 1 to 50 Mb/s has been fabricated in a 1.75-μm CMOS process. The technology choice resulted in a high level of integration compared with similar bipolar technology receivers. The measured minimum signal current for a 10^-9 bit error rate at 50 Mb/s is 48-nA r.m.s. Automatic gain control gives the receiver an electrical input dynamic range of greater than 60 dB. The outputs are TTL (transistor-transistor logic)-compatible and the chip dissipates less than 500 mW when switching at maximum speed. The die area is 16 mm² . A comprehensive noise analysis of the receiver front end provides insight into the design tradeoffs of optical receiver preamplifiers. A wideband precision amplifier used in the linear channel is discussed in detail. A simple method for recovering low-frequency signal information lost in AC coupling is described     

Effects of laser phase drift on coherent optical CDMA

Code division multiple access (CDMA) has been proposed for use in fiber high speed point-to-point systems. Previous research into CDMA has centered on completely coherent detection, that is, when the phases of all users in the system are known or tracked. While coherent detection is a reasonable assumption in many radio frequency systems, semiconductor lasers suffer from serious phase variation that makes tracking of all phases difficult to accomplish. This paper examines the effects of phase drift on several multiuser detectors for binary phase shift keying (BPSK), as well as two detectors for binary frequency shift keying (BFSK). It is shown that when the desired user's phase can be tracked, BPSK match filtering offers better bit error rates than BFSK, and closed form solutions for the asymptotic error probabilities are derived. When there is no phase tracking, it is shown that the probability of error of the multiuser detectors approaches one half. The analysis is based on a proof of the asymptotic normality of the interference caused by even a single undesired user. All asymptotic results are for infinitely long spreading codes that can be modeled as a random sequence of plus and minus ones. Whether or not the desired user's phase is tracked, all receivers examined suffer from the near-far problem     

Dependence of optical receiver sensitivity, in a 147-Mbit/sheterodyne DPSK system, as a function of optical and electricalparameter variations

Measurements of the changes in optical receiver sensitivity are described. They are caused by (a) the effect of bandpass and low-pass filtering, (b) the dependence on integer and noninteger values of the intermediate-frequency-to-bit-rate ratio, (c) the influence of the local oscillator power, and (d) the impact of deviation from ideal π phase-shift modulation. The studies were conducted at λ=1.523 μm and at a bit rate of 147.75 Mb/s, using external-cavity lasers with negligible phase noise. The results demonstrate the conditions for optimum DPSK system performance in the absence of laser phase noise. The receiver degradation observed for deviations from optimal electrical and optical conditions have been measured and found to be in good agreement with earlier theoretical calculations of microwave phase modulated schemes     

5 Gbit/s direct optical DPSK modulation of a 1530-nm DFB laser

5 Gb/s direct optical differential-phase-shift-keying (DPSK) modulation of a 1530-nm distributed feedback (DFB) laser is demonstrated using injection current modulation with a bipolar signal format. Delay demodulation is performed using an interferometer with a delay time T equal to the duration of one bit. The input and differentially encoded nonreturn to zero (NRZ) signals are shown. The bipolar modulation current signal is basically the time derivative of the NRZ signal. There was no degradation of the optical DPSK signal due to thermal frequency modulation of the laser. The direct DPSK modulation technique avoids the insertion loss and systems complexity of external DPSK modulators     

Influence of the nonlinear phase and ASE noise on DPSK balanced optical receiver in optical fiber communication system

The analytical expression of bit error probability in a balanced differential phase-shift keying(DPSK) optical receiver considering nonlinear phase noise and EDFA ASE noise is given,which is very useful to estimate the performance of DPSK balanced and unbalanced receiver in optical communication system.Through analysis,if only nonlinear phase noise is considered,both the balance and unbalanced receivers have the same performances.But if adding the ASE noise of EDFA,the balanced receiver is better.     

Balanced phase diversity receiver in 565 Mbit/s DPSK transmission system

565 Mbit/s DPSK optical transmission experiments with a balanced phase diversity receiver are reported. by employing a bulk optical 90 degrees hybrid in the input stage and a silicon bipolar multiplier IC in the demodulator and AFC stages, a system with a receiver sensitivity of -48.5 dBm and long-term stability was realised.<>     

A 45-Mbit/s CMOS VLSI digital phase aligner

An eight-channel, 45-Mb/s digital phase aligner (DPA) has been fabricated in 2-μm CMOS. The device receives asynchronous serial data at a known average clock frequency and unknown phase, and phase-aligns it with a local clock of the same frequency for subsequent synchronous processing. The all-digital architecture of this device minimizes the need for external components and avoids reliance on analog MOS circuitry. Tracking over a phase excursion range of ±4-bit periods has been demonstrated     

系统偏差对激光相干合成效果的影响

以两高斯光束相干合成建立理论模型,数值模拟和分析了在不同系统误差条件下,非共轴的阵列相干合成与共轴相干偏振合成的远场特性.结果显示,两种相干合成在同种系统误差中,不同误差值范围内分别显示不同的合成效果.     

Operation trial of 400 Mbit/s submarine optical transmission system

The letter reports the 8000 m deep-sea trial of a 400 Mbit/s submarine optical system, FS-400M, which was carried out in the Ogasawara trench in November 1984. Two repeaters fully integrated by six monolithic ICs, and 28 km-long submarine cables were used. In addition to transmission experiments for repeater spacing of 40 km, repair operation was simulated to confirm operational feasibility of the FS-400M.     

Effects of laser phase noise on the performance of optical coherent receivers

Laser phase noise (LPN) plays an important role in optical coherent systems. Based on the algorithm of Viterbi-Viterbi carrier phase estimation (CPE), the effects of LPN imposed on the coherent receivers are investigated for quadrature phase shift keying (QPSK), 8 phase shift keying (8PSK) and 16-quadrature amplitude modulation (16-QAM) optical coherent systems, respectively. The simulation results show that the optimal block length in the phase estimation algorithm is a tradeoff between LPN and additive white Gaussian noise (AWGN), and depends on the level of modulation formats. The resolution requirements of analog to digital converter (ADC) in the coherent receivers are independent of LPN or the level of modulation formats. For the bit error rate (BER) of 10-3, the required bit number of ADC is 6, and the gain is marginal for the higher resolution.     

Effect of semiconductor laser phase noise on BER performance in an optical DPSK heterodyne-type experiment

We report the first experimental investigation of the effect of laser-diode phase noise on the error-rate performance in a PSK heterodyne differential detection fibre communication experiment. A newly designed AlGaAs laser emitter with adjustable linewidth is used as both the signal carrier and the local oscillator. Error rate is measured for 25 Mbit/s and 50 Mbit/s signals at an intermediate frequency of 250 MHz, and a BER (bit error rate) of 10?10 has been achieved.     

Probability of error for optical heterodyne DPSK system with quantum phase noise

An expression is derived for the probability of error in an optical heterodyne DPSK system, subject to shot noise and quantum phase noise of the optical sources. Results are given for the maximum linewidth of the transmit and local optical sources to satisfy a given degradation in optical receiver sensitivity.     

Performance of coherent DPSK free-space optical communication systems in K-distributed turbulence

Closed-form solutions for the bit-error rate of a freespace, heterodyne optical communication system is derived when the optical beam is subjected to K-distributed optical turbulence. It is assumed that the scintillation index is confined to the range (2,3) or that the number of scatterers in the propagation path is a random variable.     

The impact of laser phase noise on the coherent subcarriermultiplexing system

In coherent optical subcarrier multiplexing (CSCM) systems, the laser phase noise may cause signal spectrum broadening and hence, causes significant deterioration in the system performance. The impact of phase noise on the CSCM system is analyzed in terms of carrier-to-noise ratio, intermodulation distortion, and adjacent channel crosstalk. The optimal modulation index and carrier to noise ratio are also presented. Some numerical results are outlined     

400Gbit/s光模块的技术浅析

随着IEEE 802.3ba标准的制定完成,100Gbit/s以太网技术已经得到验证并标准化。400Gbit/s以太网和OTN(光传输网)标准成为了下一步人们关注的焦点。文章基于现行100Gbit/s标准,讨论了双载波偏振复用的16QAM(正交幅度调制)、阵列相干探测等以太网和OTN的400Gbit/s光网络模块相关技术。     

Low detection penalty in an optical DPSK heterodyne system using asaturated optical amplifier as phase modulator

A model established from the rate equations of a near traveling-wave optical amplifier (NTWOA) used as a phase modulator shows that the modulation rate is limited by the carrier lifetime to 500 Mb/s and that the worst-case detection penalty is about 0.7 dB. It is then experimentally demonstrated that close control of the injected light polarization can reduce the detection penalty in a DPSK (differential phase-shift keying) heterodyne system, using an NTWOA phase modulator instead of an LiNbO₃ modulator, to 0.6 dB. This device and a balance receiver have allowed the implementation of 282-Mb/s DPSK link operating at 1.522 μm over 242 km of fiber with a 3-dB margin