Charles A. Brackett

Code division multiple-access techniques in optical fiber networks. II. Systems performance analysis

For pt.I see ibid., vol.37, no.8, p.824-33 (1989). In Part I a technique based on optical orthogonal codes was presented to establish a fiber-optic code-division multiple-access (FO-CDMA) communications system. The results are used to derive the bit error rate of the proposed FO-CDMA system as a function of data rate, code length, code weight, number of users, and receiver threshold. The performance characteristics for a variety of system parameters are discussed. A means of reducing the effective multiple-access interference signal by placing an optical hard-limiter at the front end of the desired optical correlator is presented. Performance calculations are shown for the FO-CDMA with an ideal optical hard-limiter, and it is shown that using an optical hard-limiter would, in general, improve system performance. >

Acousto-optic tunable filters (AOTFs) for multiwavelength optical cross-connects: crosstalk considerations

Acousto-optic tunable filters (AOTF) have been investigated as a potential basis for multiwavelength cross-connects in optical networks. In this paper, we discuss crosstalk issues, some of which are common to other cross-connect technologies, and some of which are unique to the AOTF, which will determine the suitability of the AOTF technology for this application. In particular we show how the interactions between wavelength channels make the AOTF sensitive to switch architectures, we conclude that significant performance improvements will be required to diminish crosstalk if the AOTF is to be useful in any but small-size cross-connects, even when spare and wavelength dilation are used.

A large ATM switch based on memory switches and optical star couplers

The authors propose a large asynchronous transfer mode (ATM) switch architecture based on memory switches of the type being developed by several research groups and on optical star couplers. Fast contention resolution makes it possible to combine a number of these modules, memory switches, and optical stars in order to attain a capacity of 2.5 Tb/s. This switch architecture has a relatively small failure group size of 128 STS-3 lines out of a total of 16384. The scaling of the switch to smaller capacities is discussed, showing how tradeoffs in the various parameters can be used to overcome particular technological limitations. Fault tolerance and recovery schemes are presented, showing that with minimal increase to the switch complexity and cost, a very reasonable fault recovery scheme is available for almost every sort of failure. >

Cycles in wavelength routed optical networks

Signals in wavelength routed optical networks can oscillate in closed cycles resulting in adverse effects on network operation. In particular, amplified spontaneous emission from erbium doped fiber amplifiers can form recirculating loops that lead to amplifier saturation and oscillations. Searching, enumerating and eliminating these closed cycles becomes a problem that the network designer must address. A variety of cross-connect technologies are studied and shown to result in oscillating cycles in the network. Topological and technological approaches based on Eulerian network theory and other methods are proposed to eliminate these cycle problems.

Simultaneous and independent switching of 8-wavelength channels with 2-nm spacing using a wavelength-dilated acoustooptic switch

We have used a wavelength-dilated acoustooptic cross-connect, for independent routing of 8-wavelength channels separated by 2 nm. The individual acoustooptic switches making up this cross-connect provide low-crosstalk switching only for channel spacings of at least 4 nm. Total loss through the dilated 2/spl times/2 crossconnect is 9 dB, and crosstalk ranges from -25 to -35 dB. Switch architectures of this kind will be needed in multiwavelength networks where channel spacings are too close to be accommodated by a single multiwavelength switch.

Concepts and Issues in All-Optical Networks

The idea of all-optical networks, in which signals traversing the network remain in optical form until they reach their destination, has become a focus of much research throughout the world. Included in this category are many kinds of time division, wavelength division, and code division multiple access network arrangements. Applications range from local area networks to national telecommunications networks and include optical interconnection within high speed information processors such as within digital switches.