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

Microwave subcarriers have been used to demonstrate an optical communication system suitable for the distribution of digital video channels. The design, performance, and optical link requirements are discussed for a 2-Gb/s subcarrier-multiplexed (SCM) system with 20 microwave subcarriers modulated at 100 Mb/s and using a frequency-shift-keyed format. The system uses the 2-6-GHz bandwidth and represents the first example of an SCM system using more than one octave of bandwidth. The bit error rate was measured for all 20 channels; results for five typical channels are shown and discussed. The performance results show that a digital SCM approach is attractive in an optical link for a multichannel wide bandwidth video distribution system made from standard microwave components. >

A 20-channel optical communication system using subcarrier multiplexing for the transmission of digital video signals

Wideband communication systems for providing voice, data, and video services to the subscriber over optical fibers are discussed. The principles of microwave-multiplexed lightwave systems are introduced, and several transmission experiments that demonstrate the concepts are described. >

Microwave subcarrier multiplexing: new approach to wideband lightwave systems

For the last fifteen years the attention of the fibre-optic community has been principally focused on developing baseband digital transmission system for transmitting time-division-multiplexed voice channels over long distance and interoffice routes. Attention has now shifted to extending the fibreoptic network to the subscriber loop and to providing a multitude of new services through lightwave networks.



Based on the results reviewed here, it is apparent that microwave-multiplexing techniques provide a new and attractive way to transmit wideband services over optical fibre. By allowing lightwave systems designers to use and combine the complete range of available electronics, including both analog and digital electronics, and both baseband and microwave techniques, a great number of new possibilities arise for exploiting the bandwidth of lightwave components and for designing wideband lightwave networks. Over the next few years the microwave-multiplexing techniques described in this article may fundamentally change the way we use lightwave technology.

Microwave‐multiplexed lightwave systems: A new approach to wideband networks

In this paper, we examine the trend to symbiosis and convergence of microwave, optoelectronic and lightwave technologies in communication and other closely related systems, such as radars. We outline the bandwidth limitations of optical fibre links employing semiconductor optical sources and detectors and review the properties of optoelectronic devices relevant to high-speed communication. We consider transmission of digital as well as analogue signals. We give examples of microwave/optical communication systems and discuss the possibilities of creating new network architectures based on synergy of microwave and optical technologies.

Mergence of Microwave and Optical Technologies in Communications

Fiber-coupled diode laser and photodetector microwave packages with performance extending to 20 GHz have been developed for optical tranmission of broadband analog and digital signals. These units provide all the features expected in field-deployable hermetic modules. The laser package1 incorporates a thermoelectric heat pump, thermistor, and photodetector for laser stabilization and is operable to an ambient temperature of 60°C. Microstrip coupling from the rf port to the laser chip minimizes parasitic elements and allows either direct connection to the laser or 50-Ω impedance matching over the entire band with a minimum return loss of 10 dB. The laser is coupled to a single-mode tapered lensed fiber fly-lead with solder-fixed fiber alignment. The photodetector package utilizes a substrate-illuminated mesa-geometry InGaAs PIN photodiode which terminates the rf port of the package (Fig. 1).

J. Schlafer

Papers

Design and performance of diode laser and photodetector microwave packages