Intensity noise in ASK coherent lightwave receivers

The effect of local oscillator intensity noise on the performance of two and three-branch ASK homodyne receivers and single-branch ASK heterodyne receivers is investigated and an optimum local oscillator power is found. At optimum local oscillator power, both the three-branch and heterodyne receivers are found to have a somewhat better sensitivity than the two-branch receiver. If the local oscillator power is high than the optimum value, the three-branch receiver is significantly less sensitive to intensity noise than the other two receivers     

Design of wide-band optical heterodyne balanced mixer receivers

The optical heterodyne balanced mixer, or dual-detector receiver, offers significant advantages over a single detector receiver. Balanced mixer receivers are particularly attractive for use in optical heterodyne communication systems because they conserve local oscillator power and cancel excess intensity noise present in the local oscillator. Simple circuit models that illustrate the noise performance, small signal gain, and bandwidth of a balanced mixer receiver are developed. A figure-of-merit for receiver noise performance is also derived. An example design of a gigahertz bandwidth optical heterodyne balanced mixer receiver and the techniques used to characterize near-quantum-limited receiver performance are discussed.     

Performance implications of time delay and responsivity mismatchfor balanced CPFSK lightwave receivers

The performance implications of time delay mismatch and photodiode responsivity mismatch are assessed for balanced CPFSK heterodyne receivers with differential detection. The receiver sensitivity is determined using a technique which combines computer simulation for characterizing the signal at the receiver output with a formula-based method of evaluating the bit error ratio. This approach permits consideration of laser phase noise, local oscillator intensity noise, nonlinear signal processing, and nonideal components. The numerical results quantify the penalty in receiver sensitivity due to mismatch, for different levels of local oscillator intensity noise. It is determined that time delay mismatch primarily affects the intensity noise contribution to the IF signal, while responsivity mismatch primarily affects the received signal component of the IF signal     

Impact of local oscillator intensity noise and the threshold levelon the performance of a {2×2} and {3×3} phase-diversity ASKreceiver

The impact of local oscillator intensity noise and the threshold level on the performance of the {2×2} and the {3×3} phase-diversity amplitude-shift keying (ASK) receiver has been investigated for the first time for non-Gaussian statistics. Exact equations are derived for the bit-error-rate (BER), taking into account the non-Gaussian statistics and the statistical dependency of the relative intensity noise (RIN) in the receiver branches. The results differ substantially from the case in which a priori Gaussian statistics were assumed. The sensitivity penalty of the receivers is calculated with respect to the performance of an ideal heterodyne ASK receiver for a BER of 10^-9. It is shown that for a minimum sensitivity penalty the threshold level should be chosen in relation to the local oscillator power and the intensity noise level     

Theoretical investigation of local oscillator intensity noise inoptical homodyne systems

The degradation of system performance due to the intensity noise from a semiconductor local oscillator laser is theoretically investigated. A statistical model for the optical receiver is presented to calculate the bit error rate and the power penalty resulting from the local oscillator intensity noise. The power penalty depends critically on the noise power, data rate, and spectral characteristics of the noise. Simulation results are given for homodyne systems and compared to the results of Gaussian approximation     

Analysis of a homodyne receiver using an injection-lockedsemiconductor laser

The authors study an optical homodyne receiver using an injection-locked semiconductor laser as a local oscillator. The carrier recovery process introduces a phase error, and the calculation of its statistical properties leads to the evaluation of the receiver performance. The analysis shows the dependence of the receiver performance on the injected power and the phase detuning, between the transmitter, and local oscillator electric fields. The receiver performance is affected by the phase noises of the transmitter and local oscillators, by the shot noise of the detectors in the receiver, and by the modulation noise resulting from the injection locking of the local oscillator by a modulated signal     

Optimum optical power splitting ratio of decision drivenphase-locked loop in BPSK optical homodyne receiver

In a BPSK optical homodyne receiver that utilizes a decision-driven phase-locked loop, the splitting ratio of the received power and that of the local oscillator power are very important parameters in achieving high receiver sensitivity. This paper determines the optimum setting of these parameters considering the influence of the relative intensity noise of the local oscillator and the thermal noise of the preamplifier. The optimum splitting ratio of the local oscillator power to the Q-arm is found to be 0.5. The splitting ratio of the received power to Q-arm is obtained as a function of laser linewidth. The optimum setting of the received power and the local oscillator power Is independent of the relative intensity noise of the local oscillator, the thermal noise of the preamplifier and the bit rate, At the optimum splitting ratios, required beat linewidth is obtained as 1.3×10 ^-3/T_b(τ/T_b≪1) and 2.99×10 ^-3/τ(τ/T_b≫1), where T_b is the bit duration and τ is the loop propagation delay time. We show that the total power penalty of 0.8 dB from the shot noise limit can be realized with the relative intensity noise of -170 dB/Hz and equivalent input noise current of 10 pA/√(Hz), even if an imperfect balanced receiver is utilized; quantum efficiency ratio of the twin-photodetector is 0.96, propagation time difference T/T_b is 0.01. To confirm the theoretical model, a BPSK homodyne detection experiment is performed and good agreement is found between theoretical and experimental results     

An MMIC local oscillator for 16-QAM digital microwave radio systems

The first MMIC local oscillator for 16-QAM digital microwave systems is presented. The key advance is achieving the very low phase noise required by such systems. Low phase noise is realized with a low phase noise VCO (voltage-controlled oscillator) that is installed into a new PLL (phase-locked loop). Although the developed local oscillator is 90% smaller than the existing Dielectric Resonator-based local oscillators, it achieves comparable receiver performance     

A dual-detector optical heterodyne receiver for local oscillator noise suppression

The performance of a dual-detector optical heterodyne receiver was analyzed and compared with the performance of a conventional single-detector heterodyne receiver. The dual-detector receiver is found to offer two main advantages over the single-detector receiver-1) increased performance in the presence of local oscillator intensity fluctuations that might severely degrade single-detector receiver performance, and 2) decreased local oscillator power requirements. These two advantages are particularly important in a communication system which uses semiconductor laser diodes as local oscillators. Such lasers suffer from intrinsic wide-band intensity fluctuations and can also impose strict power constraints on receiver design. Based on the analysis, suggestions for the optimal design of a dual-detector heterodyne receiver are made. Also, several experiments were performed to demonstrate the improved performance of the dual-detector receiver-both for unguided- and guided-wave receivers.     

Optimal local oscillator power in PSK homodyne systems

System performance as a function of local oscillator power and the associated intensity noise is analysed. The optimal local oscillator power depends strongly on the magnitude and spectral characteristics of the laser intensity noise. BER calculations for a 1 Gbit/s PSK homodyne system are presented.     

Etude des performances ďun récepteur homodyne à laser local synchronisé pour la détection de signaux optiques modulés en phase

An injection-locked DFB semiconductor laser can be used as a local oscillator in a receiver for phase modulated optical signals. The receiver performances are affected by phase noise of the emitter and local lasers, shot noise and the noise resulting from the local laser locking by a modulated carrier. The performances are shown to be slightly better than those of the phase-locked loop for laser linewidths below one megahertz. A design procedure for the receiver is given.     

Receiver analysis for synchronous coherent optical fiber transmission systems

A receiver sensitivity expression applicable for both PSK homodyne and heterodyne optical fiber transmission systems is derived taking account of polarization misalignment, reduced modulation depth, preamplifier thermal noise, power coupling ratio of the fiber coupler, local oscillator excess intensity noise, and reference phase errors. From a comparison of recent studies on system performance degradation due to laser phase noise a generalized expression relating beat linewidth to phase error variance for pilot carrier and Costas phase-locked-loop receivers is defined.     

Optical homodyne receiver with a six-port fibre coupler

The performance of a PSK optical homodyne system based on a six-port fibre coupler, which avoids the need for an optical 90° hybrid device, is determined. Depending on the actual receiver implementation using the coupler, the receiver sensitivity is shown to be about 0.5?3 dB from ideal and local laser excess intensity noise can be cancelled.     

8.4--A 3.39-micron infrared optical heterodyne communication system

An optical heterodyne communication system is described which employs a separate stable laser local oscillator at the receiver. The theoretical advantage of quantum-limited reception has been realized, demonstrating an improvement in receiver sensitivity of more than 40 dB over that of a conventional photodetector receiver. The fundamental sources of noise in the system are identified as laser oscillator frequency noise, atmospheric phase noise, atmospheric amplitude noise, and quantum noise. The quantitative characteristics of these noise sources are analyzed as they influence the operation of AM and FM laser communications.     

A Multibeam SIS Mixer Module for a Focal Plane Array Receiver

The integration of many receiver units into a receiver array is a common method of improvement of imaging systems. This approach, well known in the mm band for Schottky mixer arrays, has not so far been developed for Superconductor - Insulator - Superconductor (SIS) junction mixers, which give the best sensitivity in the short mm wave range and in the submm range. We demonstrate for the first time a practical low noise multibeam receiver module using SIS mixer technology. The basis for the integration of several SIS mixers with a common local oscillator source is given by the saturation of the SIS receiver noise dependence upon local oscillator power. The module comprises three identical SIS mixers integrated with a common local oscillator, coupled through a three branch waveguide directional coupler. The multibeam module has been developed for a focal plane array receiver of the 30 meter radio telescope of the Institut de Radioastronomie Millimétrique (IRAM).     

On dual optical detection: homodyne and transmitted-referenceheterodyne reception

The authors provide mathematical justification, using classical detection theory, for the observed superior performance of coherent dual optical detection over single-diode detection and establish a rationale for determining the intensity of the local oscillator. Viewing the dual detector as an optical channel with one input and two outputs, they show that in the limit of large local oscillator intensity, the optimal processor uses the difference of the two detector outputs, and consequently no bias subtraction needs to be carried out. Since phase is a major problem in applications of coherent optical communication, the authors propose modulation and detection formats that can possibly trade the effects of phase noise for the often less objectionable additive noise     

本振相位噪声对接收机性能的影响

针对工程中本振相位噪声对接收机的影响常难以估量的问题,提出利用等效相位白噪声谱密度进行评估的方法.通过分析相位噪声的产生及其对剩余误码率和动态范围的影响机理,仿真了不同相位噪声对误码率的影响程度.通过仿真结果可知:相位噪声对接收机性能具有重要的影响,工程中应针对不同的应用场合要求合理的相位噪声指标.     

A 345 GHZ heterodyne receiver for the James Clerk Maxwell Telescope

In this paper we describe the design and performance of a low-noise 345 GHz heterodyne receiver. The mixer uses a lead alloy SIS tunnel junction mounted in reduced height rectangular waveguide and is tuned with a single backshort. Local oscillator power is provided by a broad-band Gunn oscillator which drives a frequency quadrupler. The heterodyne performance has been verified in the laboratory using a gas absorption cell. In November 1991 this receiver was successfully commissioned and by direct comparison with a Schottky diode receiver we confirm a best receiver noise temperature of 150K (DSB) at 355 GHz and a tuning range of 300 to 380 GHz. The receiver is now available as a JCMT facility instrument.     

Sensitive 50-Ω coherent lightwave receiver utilizing ahigh-power local oscillator

The performance of a simple 50-Ω balanced receiver suitable for use in multigigabit heterodyne coherent lightwave systems is described. A high-power, tunable, distributed-Bragg-reflector laser is used as a local oscillator, resulting in a thermal noise penalty of only 2.4 dB. Frequency-shift keying (FSK) system results at 1 and 4 Gb/s are reported