The frequency response of a group of 1.3 μm InGaAsP vapor-phase-regrown buried heterostructure lasers of various cavity lengths is analyzed by fitting the measured response curves. The dependence of resonant frequency f 0 and damping rate \Gamma on bias power is determined. The differential gain coefficient for InGaAsP is determined as 3.5 \times 10^{-16} cm2. The damping rate is found to be proportional to the square of the resonant frequency with a proportionality factor which is independent of device geometry and facet reflectivity. The existence of such a universal relationship between \Gamma and f 0 and the observed magnitude of the damping rate is explained by the interband relaxation model of nonlinear gain.

Frequency response of 1.3&#181;m InGaAsP high speed semiconductor lasers

Microwave subcarrier multiplexing (SCM) is an important approach to the design of lightwave systems for broadband distribution. Recent progress in the design and performance of both analog and digital multichannel SCM systems is reviewed. The application of broadband SCM systems to both passive and optically amplified distribution networks is discussed. The discussion covers the general features of SCM systems; the electrooptic components that have been used in the system experiments described here, including laser intensity noise and noise due to intermodulation products; the carrier-to-noise ratio requirements; some multichannel FM systems experiments; and a 20-channel digital systems experiment; and a hybrid system carrying 60 FM SCM channels plus a 100-Mb/s baseband digital channel. Several approaches to broadband subscriber distribution networks are analyzed. >

Subcarrier multiplexed lightwave systems for broad-band distribution

Applications for subcarrier multiplexing include a variety of analog and digital lightwave transmission systems. An overview of the requirements and capabilities of these systems is presented by describing specific examples of the most popular system types. These examples include multiuser interactive local area networks and multichannel digital, FM, and AM-VSB (vestigal sideband) video distribution systems. Limitations imposed on each by the linearity of directly or externally modulated sources, receiver noise, and relative-intensity noise are discussed. >

Subcarrier multiplexing for lightwave networks and video distribution systems

This paper describes the applicability of subcarrier multiplexing to lightwave multiple-access networks. It is shown how currently available microwave and lightwave components can be used, by using subcarrier multiplexing, to provide high-capacity networks. For example, the proposed multiple-access network can support 1024 users at a continuous bit rate of 1.5 Mbit/s, per user.

Subcarrier multiplexing for multiple-access lightwave networks

The phase noise associated with single-mode semiconductor lasers must be accounted for in performance studies of lightwave communication systems. The standard phase noise model is a Brownian-motion stochastic process. Although many analyses of lightwave communication systems have been published, none, to the authors knowledge, has fully adhered to the standard model. The reason is that a proper characterization of filtered lightwave signal had not been achieved. Such a characterization, along with theoretical approaches to obtaining it, is detailed. The authors show, for example, how to generate probability density functions (PDFs) of the magnitude of a filtered laser tone (with special attention to the tail region) and how to analytically represent the characteristic function of the PDF in closed form in the small-phase-noise realm. With the characterization in place, the stage is now set for determining the bit-error rate performance of advanced detection techniques which seek to mitigate the phase noise impairment. >

Characterizing filtered light waves corrupted by phase noise

We present a demonstration of subcarrier multiplexing in a lightwave multiple-access network. Three 44 Mbit/s digital signals are transmitted along a single-mode fibre bus by intensity-modulating two 1.3 μ-wavelength, multimode laser diodes with FSK subcarriers, at frequencics between 3.5 and 4.0 GHz. Intermodulation distotion, generated when two or more subcarriers are transmitted by the same laser, does not degrade the tranmission quality.

Lightwave system using microwave subcarrier multiplexing

We report the dependence of receiver sensitivity on laser linewidth for a series of ASK heterodyne experiments performed with 1.5 ?m distributed feedback lasers and external cavity lasers, and the result of an error-free heterodyne transmission experiment at 150 Mbit/s over 102 km of fibre using the external cavity lasers.

Performance of ASK heterodyne detection for various laser linewidths

Electrical and optical measurements on ZnS : Mn, Cu-dc electroluminescent (DCEL) powder panels are reported. It is shown that current conduction in these devices depends upon avalanche breakdown in a thin insulating Cu-depleted layer of phosphor of thickness up to approximately 1 µm. However, it is concluded that the overall current-voltage characteristics of a panel are determined by the various components external to this layer. That the current density throughout this layer is highly nonuniform is deduced and the consequences of this result are discussed in terms of the effect on saturation brightness. A new model to explain the details of the observed electrical behavior of DCEL powder panels is introduced and compared with previously proposed models. Finally the various failure modes observed in these devices are identified and their elimination is discussed.

An investigation of the electrical and optical properties of DC electroluminescent ZnS:Mn, Cu-powder panels

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 pi phase-shift modulation. The studies were conducted at lambda =1.523 mu m 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. >

Dependence of optical receiver sensitivity, in a 147-Mbit/s heterodyne DPSK system, as a function of optical and electrical parameter variations

Crosstalk penalties as a function of channel spacing were measured in a two-channel ASK heterodyne system using 1·55μm DFB lasers. For an IF linewidth/bit rate ratio of 0.5, the channel spacing in the IF domain must be greater than 13 times the bit rate for negligible crosstalk penalty.

M. Dixon

Papers

Lightwave system using microwave subcarrier multiplexing

Performance of ASK heterodyne detection for various laser linewidths

An investigation of the electrical and optical properties of DC electroluminescent ZnS:Mn, Cu-powder panels

Dependence of optical receiver sensitivity, in a 147-Mbit/s heterodyne DPSK system, as a function of optical and electrical parameter variations

Crosstalk penalty in a two-channel ASK heterodyne detection system with non-negligible laser line width