Definition

Space switch fabric architecture is shown in figure. The switch consists of N incoming and N out going fiber links, with n wavelengths running on each fiber link. The switch is slotted, and the length of the slot is such that an optical packet can be transmitted and propagated from an input port to an out put optical buffer.

The switch fabric consists of three parts; optical packet encoder, space switch, and optical packet buffer. The optical packet buffer works as follows. For each incoming fiber link, three is an optical demultiplexer, which divides the incoming optical signal to different wavelengths. Each wavelength is fed to a different tunable wavelength converter ( TWC), which converts the wave length of the optical packet to a wavelength that is free at the destination optical output fiber. Then, through the space switch fabric, the optical packet can be switched to any of the N out put optical buffers.

Specifically the out put of a TWC is fed to a splitter, which distributes the same signal to N different out put fibbers, one per out put fibber. The signal on each of these out put fibbers goes through another splitter, which distributes this in to d+1 different out put fibbers, and each out put is connected through an optical gate to one of the ODLs of the destination out put buffer. The optical packet is forwarded to an ODL by appropriately keeping one optical gate open and closing the rest. The information regarding to which wavelength of an incoming packet and the decision as to which ODL of the destination out put buffer the packet will be switched to is provided by the control unit, which ahs knowledge of the state of the entire switch.

Each out put buffer is an optical buffer implemented as follows. It consists of d+1 ODLs, numbered from 0 to d. ODL1 delays optical packet for a fixed delay equal to 1 slots. ODL0 provides zero delay, and a packet arriving at this ODL is simply transmitted out of the out put port.