Optimum system design for CPFSK heterodyne delay demodulationsystem with DFB LDs

An optimum system configuration for an optical continuous-phase frequency-shift-keying (CPFSK) heterodyne delay demodulation system with distributed feedback laser diodes (DFB LDs) is discussed. The optimum modulation index was determined by evaluating the LD phase noise effect and the IF noise effect. The IF noise effect was investigated in detail, considering the noise conversion effect through delay demodulation. In the case of 10-MHz IF beat spectral width, the modulation index m =1.5 is optimum for a 1.2-Gb/s system. With this optimum modulation index, a 204-km long-span transmission experiment, with -41.5 dBm receiver sensitivity, has been successfully performed. The feasibility of using stand-alone DFB LDs for a high-sensitivity CPFSK delay demodulation system has been confirmed through this experiment     

Long-span optical FSK heterodyne single-filter detection transmission experiment using a phase-tunable DFB laser diode

High receiver sensitivity (?51.9 dBm) and long span (243 km) transmission expriments have been achieved with a 140 Mbit/s optical FSK heterodyne single-filter detection system, using a phase-tunable DFB laser diode as a transmitter. This has enabled direct FSK modulation without waveform distortion. Also, a 280 Mbit/s 204 km transmission experiment has been carried out successfully.     

Balanced operation of a GaInAs/GaInAsP multiple-quantum-wellintegrated heterodyne receiver

The balanced operation of a multiple-quantum-well balanced heterodyne receiver photonic integrated circuit (PIC) is described. Using only SMA-connected 50 Ω commercial electronics, a free-space beam sensitivity of -42.3 dBm at 108 Mb/s and -39.7 dBm at 200 Mb/s for NRZ FSK (frequency-shift keying) reception has been achieved. This represents a 14 dB improvement over any previous heterodyne receiver PIC sensitivity. In addition to providing the multichannel benefits of heterodyne reception, this is also the highest sensitivity yet reported for any OEIC (optoelectronic integrated circuit) receiver     

System design and long-span transmission experiments on an optical FSK heterodyne single filter detection system

The influence of LD phase noise on a heterodyne noncoherent detection system was evaluated. Based on the evaluation, an optical FSK heterodyne single filter detection system with large frequency deviation and wide-band IF filter has been developed to allow use of stand-alone DFB LD's. In the system, a phase tunable DFB LD was used as an FSK transmitter light source to improve the FSK modulation characteristics. An IF filter with appropriate bandwidth evaded the influence of LD phase noise. With these configurations, long-span (243 km at 140 Mbit/s and 204 km at 280 Mhit/s) transmission experiments have been successfully carried out on this single filter detection system. To the contrary, influence of LD phase noise appeared in a limited IF bandwidth case, which agrees well with the theoretical evaluation.     

FSK heterodyne transmission experiments at 560 Mbit/s and 1 Gbit/s

Optical frequency-shift-keying (FSK) signals are obtained from directly modulated distributed feedback (DFB) semiconductor lasers. Experimental studies of the direct frequency modulation (FM) characteristics of the DFB lasers show a nonuniform FM response due to the competing effects of thermal modulation of the laser active region and carrier density modulation. Equalization of the signal current to the laser is employed to produce a flat FM response from 30 kHz to 1 GHz. Optical FSK transmission and heterodyne detection experiments at 560-Mbit/s and 1-Gbit/s are conducted at a wavelength of 1497 nm. Receiver sensitivities of -39 dBm at 560 Mbit/s and -37 dBm at 1 Gbit/s are obtained. Transmission through 100 km of single-mode fiber at 1 Gbit/s is achieved with no degradation in receiver sensitivity.     

FM response of InGaAsP buried heterostructure distributed feedbacklasers and their applications in incoherent FSK systems

Measurements are reported of the frequency modulation (FM) response of InGaAsP buried heterostructure distributed feedback (DFB) lasers and the system performance of a 1.7-Gb/s and 622-Mb/s incoherent frequency-shift-keyingn (FSK) system using these lasers. The measured lasers include 1.55-μm conventional DFB lasers and quarter-wave shifted DFB lasers. The thermal dips in the FM response of quarter-wave shifted DFB lasers usually occur at the lower frequencies, compared with that of conventional (250-μm-long) DFB lasers. A receiver sensitivity of -32.5 dBm (-39.5 dBm) for a 1.7-GB/s (622-Mb/s) incoherent frequency-shift-keying (FSK) system was achieved using a quarter-wave shifted DFB laser     

Monolithic balanced p-i-n/HBT photoreceiver for coherent optical heterodyne communications

Two InGaAs p-i-n photodetectors connected in a balanced configuration have been monolithically integrated with a transimpedance preamplifier made from InP-InGaAs heterojunction bipolar transistors (HBTs) to realize a balanced optoelectronic integrated circuit (OEIC) receiver. The receiver, with a bandwidth of 3 GHz and a common mode rejection of 25 dB, has a sensitivity of -49 dBm at a bit error rate of 10/sup 9/ under NRZ FSK reception at 200 Mb/s.<>     

Bipolar optical FSK transmission experiments at 150 Mbit/s and 1Gbit/s

Bipolar direct modulation has been used to overcome the nonuniform low-frequency modulation response of distributed-feedback laser transmitter in optical FSK transmission experiments at 150 Mb/s and 1 Gb/s. The heterodyne receiver sensitivity was -48 dBm for 150 Mb/s and -39 dBm for Gb/s, independently of the pseudorandom pattern length. There was no degradation in receiver sensitivity with transmission through more than 100 km of fiber     

1 Gbit/s bipolar optical FSK transmission experiment over 121 km offibre

Bipolar direct modulation has been used to overcome the nonuniform low-frequency modulation response of a DFB laser transmitter in a 1 Gbit/s optical FSK transmission system. The heterodyne receiver sensitivity (nP¯) was -39 dBm for a 2²³-1 bit pseudorandom pattern, with no degradation in receiver sensitivity after transmission through 121 km of fibre     

140Mb/s混合集成激光器驱动模块

140Mb/s LD驱动器模块包括Si双极耦合逻辑开关缓冲、整形放大、LD驱动器和LD组件三部分。采用混合集成平面微组装工艺将这三部分制作在一块30×49mm~2的陶瓷基片上。在ECL电平驱动下,光脉冲上升时间和下降时间均小于等于1ns,出纤光功率为-6dBm～-3dBm,消光比≤10％,在10~(-9)误码率下,接收机的灵敏度为-39dBm。     

140Mb/s混合集成光发射机

研制了一种混合集成140Mb/s单模半导体激光器发射机。该发射机由高速缓冲整形放大、LD驱动功能模块、LDAPC——LD自动功率控制功能模块、LDATC——LD自动温度控制功能模块,LD保护及寿命,信号终断告警功能模块和调顶功能模块所构成。发射机调制出纤光功率为-6dBm～-3dBm、消光比≤10％,在0～45℃范围内光功率变化在±1dB以内。该发射机和本所同时研制的混合集成光接收机配套,构成了目前140Mb/sPCM数字光端机的全新产品。     

High-performance monolithically integratedIn0.53Ga0.47As/InP p-i-n /JFET optical receiverfront-end with adaptive feedback control

An optical transimpedance receiver front-end that is adaptable to a wide range of bit-rates up to 3 Gb/s has been realized by monolithically integrating high efficiency p-i-n photodiodes with low noise InGaAs junction field effect transistors. The transimpedance-bandwidth product of the receiver is 2.8 THz Ω. The average equivalent input noise current for full circuit bandwidth is 4.0 pA/√Hz. The preamplifier for nonreturn to zero data transmission without equalization of the frequency response at 1.55 μm offers a sensitivity of -41.5 dBm and -29.5 dBm at 140 Mb/s and 2.4 Gb/s, respectively. The dynamic range is 17 dB at 2.4 Gb/s and exceeds 30 dB at 500 Mb/s     

Alternate-mark-inversion optical continuous phase FSK heterodynetransmission using delay-line demodulation

Alternate-mark-inversion (AMI) optical continuous phase (CP) frequency-shift keying (FSK) heterodyne transmission using delay-line demodulation which has a higher receiver sensitivity compared to the transmission using single-filter demodulation has been achieved. Since the proposed delay-line demodulation method directly converts the received AMI-CPFSK signal into the nonreturn to zero (NRZ) baseband signal without the use of an AMI decoder, a heterodyne receiver with the same configuration as the conventional CPFSK transmission system is realized, even though AMI line coding is applied to the system. Transmission experiments at 622 Mb/s have been demonstrated for both pseudorandom 2⁷-1 and 2²³-1-b patterns at the same receiver sensitivity of -41.1 dBm (the PD input power)     

Optical FSK transmission with pattern-independent 119 photoelectrons/bit receiver sensitivity and endless polarisation control

Demonstrates 140 Mbit/s FSK transmission with a -56.7 dBm receiver sensitivity. The system features endless polarisation control and Manchester coding at the transmitter to overcome the nonuniform FM response of the DFB-laser in conjunction with a highly efficient subcarrier demodulation scheme in the receiver.<>     

20 channel coherent FSK system using subcarrier multiplexing

A 20-channel multioctave coherent frequency shift keying (FSK) system using subcarrier multiplexing techniques is described. The microwave subcarriers range from 2.1 to 5.9 GHz with a 200-MHz channel spacing. The receiver consists of a p-i-n photodiode, electrical isolator, low-noise amplifier, and bandpass filter to provide channel selection. The channels are modulated at 100 Mb/s, corresponding to one digitized video channel. Results for the optimal phase modulation index and degradation due to second- and third-order intermodulation distortion are discussed. For the worst-case channel, a receiver sensitivity of -27 dBm was achieved     

140Mb/s混合集成光接收机

本文报导了140Mb/s混合集成光接收机的研制结果。接收机全部由厚膜电路集成模块组成。其主放带宽为200MHz(3dB),输出电压V_(pp)值为0.8V,接收灵敏度在10~(-9)误码率下为-39dBm。     

Sensitivity degradation in polarization diversity receivers forlightwave systems

The effect of weighting circuit unidealities on the sensitivity degradation of diversity receivers is examined for synchronous and nonsynchronous detectors. A novel model is developed in which the weighting ratio for each polarization diversity receiver branch can be calculated using practical values. For synchronous detectors, it is shown analytically that the sensitivity degradation is relatively independent of the weighting ratio deviation from the optimum value. The same is also true for nonsynchronous detectors. Results of experiments on a 600 Mb/s single-filter frequency-shift keying (FSK) lightwave system, a 400 Mb/s continuous-phase FSK (CPFSK) lightwave system, and an amplitude-shift keying (ASK) synchronous detection network simulated with a 600 Mb/s baseband system generally support the theoretical results     

High-sensitivity FSK signal detection with an erbium-doped fiberpreamplifier and Fabry-Perot etalon demodulation

A report is presented on a 622-Mb/s optical transmission system with demodulation of alternate mark invert (AMI) encoded frequency shift keying (FSK) signals by a Fabry-Perot etalon. A 25-dB gain erbium-doped fiber preamplifier gave a receiver sensitivity of -40 dBm at 10^-9 BER, which was improved to -44 dBm with the addition of a narrowband optical filter. The theoretical sensitivity of the preamplified receiver and the effect of the etalon on the amplified spontaneous emission beat noise are discussed and related to experiment     

Polarisation- and pattern-independent optical FSK heterodyne system using data-induced polarisation switching

Data-induced polarisation switching is a simple yet powerful technique to solve the polarisation problem in optical FSK heterodyne systems. The authors achieve a polarisation- and pattern-independent sensitivity of -53.5 dBm for a 140 Mbit/s FSK receiver. The response time to polarisation changes is estimated as 100 ns.<>