This paper describes theoretical analyses of a new CRV (Code Rule Violation) collision detection method applicable to an optical CSMA/CD LANs. The new method is based on the ideas combining a partial response (1,0, --1) circuit with the basic CRV collision detection method; the ideas are proposed in IEEE 802.3 committee. The circuit configuration of the new method, however, is different from that proposed in IEEE 802.3 committee. First, the paper outlines the basic CRV collision detection method and shows the problem that it can't detect a collision when identical bits are continuously received. Secondly, a practical circuit configuration of the new method is introduced. To realize large optical dynamic range and stability in collision detection, the circuit is designed not to detect CRVs on noisy zero level signals caused by signal negation with partial response circuits. The calculation formulae are then derived for the basic and the new method to determine the CRV rate with and without signal collision. At a bit rate of 10Mb/s, the CRV rate with and without signal collision is then calculated for the basic and the new method. Finally, the calculation results are compared with each other, and it is clarified that the new method is an effective method to increase CRV rate when signal collision occurs.

This paper proposes a new acknowledgement (ACK) delivery scheme performed in layer two, which gives the highest transmission priority to ACK delivery so as to enable higher ACK transmission speeds in networks using the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) access procedure. This scheme is based on the principle of confirming ACK delivery through intentional collision. That is, an ACK is determined to have been received at the source adapter when a packet collision is observed after the end frame delimiter (EFD) of the return-packet. The throughput of a non-persistent CSMA/CD using the new scheme is then analyzed. This throughput is compared to the previously-proposed Acknowledge Ethernet type scheme. The analysis indicates that the new scheme yields a throughput several percent higher than the previous one. Application of the scheme to a 32 Mbit/s fiber-optic passive star network, or SOLARnet, is outlined. The experimental results obtained in a SOLARnet field trial are also reported and discussed.

This paper describes the key areas of support network management in a fiber-optic passive star-configured local area network (SOLARnet) from the view point of lower layer functions. The network manages all network elements including communications control adapters and transmission medium. This is accomplished with a network control terminal that handles management duties such as operation, administration and maintenance. Key areas discussed are architecture and management functions that perform management duties. Management functions used by SOLARnet, together with its systematic outline and protocol are also shown. In a field test, the network operated reliably using the network management functions.

This paper describes a newly developed 22 liquid crystal optical switch for 1.3µm single-mode fiber use. This switch state can be freely set at either the cross or the bar state. The measured performance of two prototype 22 liquid crystal optical switches is given. Tests confirm that the 3 values are a maximum insertion loss of 1.5dB, a crosstalk attenuation of more than 26.1dB, and a return loss of more than 28.9dB. Requirements for optical switches for fault isolation are theoretically clarified from a LAN system view point.