Polarisation-insensitive optical heterodyne receiver for coherent FSK communications

An optical FSK heterodyne communications receiver is proposed using a polarisation diversity technique which has a reduced level of complexity. The proposed receiver is constructed and tested at 100kbit/s and shown to have a maximum fluctuation in sensitivity of 17% over conditions of originally complete polarisation fading.     

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.<>     

565 Mbit/s optical PSK transmission system with endlesspolarisation control

A 565 Mbit/s optical PSK transmission system incorporating automatic endless polarisation control is reported. A receiver sensitivity of -49.8 dBm was achieved, and the randomly varying polarisation state of the received signal was tracked with no observed degradation in system performance     

High-gain mode-adapted semiconductor optical amplifier with12.4-dBm saturation output power at 1550 nm

A mode-adapted semiconductor optical amplifier (SOA) has been fabricated and packaged. At the gain peak, 1500 nm, the fiber to fiber gain was measured to be 32.5 dB. Statistics for eight packaged devices indicate that a fiber-to-fiber gain of 26.3 dB ± 1.3 dB and a saturation output power of 12.4 dBm ± 0.4 dBm are typical at a bias of 500 mA for λ = 1550 nm. Polarization sensitivity at 1550 nm was measured to be 1.1 dB ± 0.4 dB and the transverse electric (TE) polarization state noise figure (NF) was determined to be 7.0 dB ± 0.5 dB. The coupling loss was 1.3 dB ± 0.1 dB per facet. This SOA, with a 1.3-nm filter, was used as an optical preamplifier in a 10-Gb/s return-to-zero (RZ) system testbed with a pseudorandom binary sequence (PRBS) of 2³¹ -1. A 14.5-dB improvement in receiver sensitivity was observed at a bit error rate (BER) of 10^-11     

Stabilisation of heterodyne receiver sensitivity with automatic polarisation control system

A low-insertion-loss automatic optical fibre polarisation control system with low driving voltage and low monitoring power has achieved stabilisation of the receiver sensitivity within the fluctuation range of less than 0.4 dB in an optical FSK heterodyne 280 Mbit/s, 141 km transmission experiment.     

Power penalty analysis due to polarisation diversity on 1.2 Gbit/s optical DPSK heterodyne transmission

An optical DPSK transmission experiment was performed over 100 km at a bit rate of 1.2 Gbit/s using a dual-balanced polarisation-diversity receiver. A high receiver sensitivity of less than -42.8 dBm was achieved and the power penalty due to polarisation diversity was analysed.<>     

Operation of digital optical transmission system with minimaldegradation due to polarisation mode dispersion

The probability of BER degradation above 10^-9 is evaluated theoretically as the quality parameter for examining the robustness of an optical transmission system incorporating an EDFA to fibre polarisation mode distortion (PMD). Provided that there is an existing power margin, a significantly reduced sensitivity to PMD is achieved by detuning the decision level of the optical receiver from the optimum for zero PMD     

Polarisation-diversity receiver for coherent FSK communications

A polarisation-insensitive optical heterodyne receiver, in which two signals with orthogonal polarisations are independently detected and demodulated, and subsequently combined, has been demonstrated for FSK-modulated signals at 50 Mbit/s with a sensitivity of ?55.5 dBm (Pe=10?9). The receiver uses the entire received signal and local oscillator signal with only one photodiode in each branch. Differences between the two PINFET detectors result in a ±ldBm sensitivity variation for all polarisation states of the received signal.     

Practical realization of a high density diode-coupled wavelengthdemultiplexer

The design, development, and optical performance of a novel demultiplexer in which a photodiode array replaces the array of fibers at the output is described. The prototype diode-coupler high-density wavelength demultiplexer has 16 channels with 4-nm channel spacing. Its optical performance, with respect to insertion loss, optical passband, total optical crosstalk, and polarization response and taking into account expected component and manufacturing tolerances is good. In particular, an optical passband between ±0.7 nm and ±0.9 nm can be tolerated without deterioration in performance, reducing the need for precise laser wavelength control. In addition, the diode leakage currents achieved, although relatively large, do not constitute a significant penalty in receiver sensitivity for applications at 560 Mb/s or higher, and the diode capacitance is very low. It is concluded that this is an attractive solution for high-density wavelength-division multiplexing     

Sensitivity degradation of an optical {2×2} and a {3×3}phase diversity ASK receiver due to gain imbalance and nonideal phaserelations of the optical hybrid

The sensitivity penalty due to phase and gain imbalance for a {2×2} and a {3×3} optical homodyne phase diversity amplitude-shift keying (ASK) receiver is investigated for the shot-noise-limited case. It is shown that both types of imbalance lead to a time varying character of the bit error rate (BER) types of imbalance and the phase mismatch. The calculation of the BER is performed as a function of the threshold value. It is shown that for an optimized threshold value, the phase diversity ASK receivers can tolerate rather large amounts of gain imbalance, namely approximately ±10%, and a phase mismatch of approximately ±10° for the {2×2} receiver and approximately ≠15° for the {3×3} receiver without an excessive sensitivity degradation (<2 dB)     

Polarisation-independent wavelength conversion using nonlinearoptical loop mirror

A polarisation-independent all-optical wavelength conversion technique is proposed that uses a nonlinear optical loop mirror (NOLM). When the polarisation state of the input signal light is varied, wavelength-converted signals exhibit a converted power fluctuation of only 0.6 dB, and the receiver sensitivity does not change     

0.15 dB/cm loss in Unibond SOI waveguides

The optical loss of Unibond waveguides is measured and reported for the first time, using grating couplers. At a wavelength of 1.3 μm, a loss of 0.15±0.05 dB/cm is obtained for TE polarisation. This allows good quality low loss integrated optical circuits to be fabricated at low cost     

Feasibility study on common polarisation control for coherent FDM transmission system

A common polarisation control with a single polarisation controller for a coherent optical FDM transmission system is proposed. This scheme is applicable to the system carrying 600 Mbit/s-16 channel to 5 Gbit/s-2-channel coherent FDM signals, with a great reduction in receiver complexity.<>     

90° SOI optical hybrid for Radio-over-fibre links

Radio-over- fibre (RoF) technology is receiving large attention due to its ability to provide simple antenna front ends, increased capacity and increased wireless access coverage. Coherently detected RoF systems would enable the information to be carried in both the amplitude and phase or in different states of the polarisation of the optical field. Additionally, the selectivity of coherent receiver is very well suited for access networks. We present a 90° optical hybrid built on a silicon-on-insulator planar light-wave circuit, which can be used as the optical front end of the digital coherent receiver in a digitised RoF link and will lead to reduced receiver footprint and cost. The optical hybrid circuit includes 2?×?2 and 4?×?4 multimode interference (MMI) splitters, in a polarisation diversity configuration. The simulation results at vacuum wavelength 1,550 nm show polarisation independence and phase errors between the ports of less than 0.03°. The properties of the prototyped 4?×?4 MMI were measured over a wide range of wavelengths. The 2?×?2 and 4?×?4 MMI showed nearly equal splitting ratios. Measurements of the relative phase relationship between the ports for Transverse Electric mode polarisation are shown to match the simulation results.     

Si基单片集成850nm光接收芯片研究

设计并制备了一种Si基单片集成850nm光接收芯片,包括"P+/N-EPI/BN+"结构的光电探测器(PD)、跨阻前置放大电路及其后续处理电路。分析了PD的结构,并对其光谱响应及频率响应进行模拟,在2.0V偏压下,PD在850nm的响应度为0.131A/W,截止频率为400 MHz。采用0.5μm BCD(bipolar、CMOS和DMOS)工艺流片,光接收芯片面积约为900μm×1 100μm。测试结果表明,PD暗电流为pA量级,响应度为0.12A/W。光接收芯片在155 Mb/s速率及误码率(BER)小于10-9情况下,灵敏度为-12.0dBm;在622 Mb/s速率及BER小于10-9情况下,灵敏度为-10.0dBm,并能得到清晰的眼图。将该光接收芯片封装后接入光接收模块,进行点对点光互联实验,获得很好的光信号通路。     

High-dynamic-range airborne tracking and fire control radarsubsystem

Two high-dynamic-range receiver subsystems for use in airborne radar fire control and tracking applications are described. The X -band dual-channel monopulse tracking receiver operates at 9.36±0.290 GHz with a 6-dB noise figure and a linear instantaneous dynamic range of 42 dB. A total of 80 dB of RF and IF gain control is programmable with less than ±15° phase and ±1 dB amplitude tracking errors. The Doppler radar receiver operates at 9.3±0.15 GHz and has a 4.6-dB noise figure with ⩾80 dB of instantaneous dynamic range. An 18-dB sensitivity time control (STC) circuit and a 60-dB dump attenuator allow close-in target reception     

First low polarisation dependence optical FSK receiver based on a Fabry-Perot laser with a near square active waveguide structure

A low polarisation dependent optical FSK receiver based on an FP laser with one antireflection coated facet and a near square active waveguide structure is reported. The FP laser receiver presents a polarisation-dependence of less than 2 dB.<>     

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.<>     

光收发模块眼图、消光比及灵敏度关系的实验研究

光接收灵敏度与光发射信号的消光比大小和眼图的上升沿/下降沿陡度具有紧密相关性，试验研究表明，155Mbps光收发模块消光比在16-20dB之间时光接收灵敏度最佳，眼图的上升沿/下降沿陡度越陡越好，一般情况下随上升沿/下降沿陡度的变化光接收灵敏度具有2-3dB的差异。     

Polarisation mode dispersion tolerance of 10 Gbit/s NRZ and RZoptical signals

The authors have evaluated the performance of an optical receiver with polarisation mode dispersion (PMD) for non-return-to-zero (NRZ) and return-to-zero (RZ) signals at 10 Gbit/s, and found that the RZ format is more tolerant to PMD than is the NRZ format