The hardware and the communication protocol of a scalable optical ring have been designed. A hardware routing has been achieved on the network interface card to minimize data packet communication latency and a simplified communication protocol has been designed to reduce communication overheads. To reduce the data packet bilking probability and have a more efficient usage of the data link layer bandwidth, a virtual multi-channel transmission mechanism has been achieved. The network supports a maximum of 16 virtual channels for each physical data link. Time slots can be dynamically assigned to each virtual channel. Zero wait time has been achieved for the switching between different virtual channels.

distributed polarization coupling in high birefringence fibres. Detailed theoretical analysis of the measurement accuracy of the testing system is presented. The main part is a Michelson interferometer with a scanning arm driven by a stepping motor. The minimum polarization coupling intensity detectable by this system is-77 dB. The maximum fibre length that can be tested under this design is more than 1 km, and the spatial resolution is better than 50mm. The influence of the opto-electro-mechanical devices on measurement accuracy has been analysed in order to improve the performance-to-cost ratio. This testing system can also be used in coherence division multiplexing optical fibre sensors.

A multichannel ring is designed. Each sublayer network is connected to the ring with an access node (AN). which can transmit data at every wavelength with a tunable laser diode The data transmission speed at each wavelength is 1.25 Gbit/s. With eight waverengths, a total bandwidth of 10 Gbit/s can be obtained. With a bandpass filter, the desired optical signal can be dropped down at the access node. On receiving a data packet, the optical signal is split into two parts One part is converted to an electrical signal and its destination address is extracted and verified, if the data packet belongs to the local subnetwork, it is received. Otherwise, it is retransmitted to the next access node with a selected wavelength. So pipelining data transmission can be achieved among different wavelengths And this nelwork is a multipipelie structure. The data processing time is less than 3OO ns, and all of the pro cessing procedure is implemented via a field programmable gate array (FPGA). So the communication latency and communication overheads can be decreased. Meanwhile, the ring topology has good eatabillity More wavelengths can be adopted for a large-scale network with more access nodes.

The insertion loss of a fiber optical rotary joint depends on the mechanical misalignments of the collimating lenses. To achieve 3-dB or lees insetion loss, the lateral misalignment of the braded-index (GRIN) lenses should be less than 100μm, and the angular tilt of these lenses is limited to 0.1 deg. These requirements cause a high mechanical abrication and assembly cost. To solve this problem. We design a singlechannel optical rotary joint using a bulk optical detector. The requirement on lateral misalignment is relaxed to 500μm, and the angular tilting is relaxed to 2 deg. Using this method, the cost of the optical rotary joint can be dramatically reauced.

In this paper, a communication protocol has been designed for the two-layer scalable optical interconnectinn network (TgOlNet) designed in Tianjin University. The communication protocol has been designed based on TCP/IP (transmission control protocol/intemet protocol) protocol. But it is more efficient than TCP/IP for data Iransmissinn in TSOINet. An auxiliary channel has been introduced in TSOINet for transmission of the commtmicatinn status messages among the sub-layer rings. Many network management functions, such as flow control, hand shaking, etc., can be achieved via the auxiliary chalmel, so the commtmication overheads can be decreased. The performance of the corrtmunication protocol has been evaluated compared to TCP/IP protocol for data transmission in TSOINet.

A novel structure has been designed for bit synchronization in a terabit-per-second optical interconnection network with adjustable optical delay lines, The two-stage network consists of 1024 optical links connected to a central switching module. A distributed optical clock network is designed for bit synchronization at each node computer. Zero link setup time can be achieved by precisely atching the phases of each pair of clock and signal. The link-to-link switching time can be reduced to less than 20 ns in the two-stage network. Even in a three-stage network that can accommodate 32,768 optical links, the link switching time can be maintained below 30 ns. At the same time, a tetal bidirectional band width of 98.304 Tbit/s can be obtained. Since bit synchronization is achieved entirely in the optical domain, this structure is independent of link transmission rates.

Piezo-electronic transducer is used in combination with mechanical scanning devices to improve measurement accuracy in a distributed polarization coupling detection system. For mechanical scanning range of 150mm with 200-nm resolution, the measurement error of polarization-coupling intensity can be improved from 38% to 2% in combination with a 20-nm resolution piezo-electronic transducer.

White light interferometry has been adopted to measure distributed polarization coupling in high-birefringence waveguides. Since the coupling mode is weak compared to the exciting mode, the contrast ratio of the interferogram is very low. This will increase the difficulty of direct detection of the polarization coupling intensity. By rotating the angle between the polarization eigenmodes and the principal axis of the linear polarizer from 45

A new structure for bit synchronization in a tera-bit/s optical interconnection network has been designed using micro-electro-mechanical system (MEMS) technique. Link multiplexing has been adopted to reduce data packet communication latency. To eliminate link set-up time, adjustable optical delay lines (AODLs) have been adopted to shift the phases of the distributed optical clock signals for bit synchronization. By changing the optical path distance of the optical clock signal, the phase of the clock signal can be shifted at a very high resolution. A phase-shift resolution of 0.1 ps can be easily achieved with 30-μm alternation of theoptical path length in vacuum.

A broadband optical rotary joint (BORJ) was designed using Clenses. Its insertion loss was less than 2 dB at both the 1300nm and 1550nm wavelength windows. Wavelength division multiplexing (WDM) technique was adopted to increase the number of data transmission channels. Hundreds of wavelength channels can be accommodated for data transmission through relatively rotating interfaces using this BORJ. The total data transmission rate through this BORJ can be more than 200 Gbit/s. By using Dove prism, both space division multiplexing (SDM) and WDM techniques can be implemented simultaneously in the design of BORJ with C-lenses. This structure of BORJ has a low cost. It can be used for optical data transmission and optical sensing.