Optical time slot interchanger apparatus and method of operation
AssigneeAT&T Corp.
InventorRonald A. Spanke
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Abstract
An Optical Time Slot Interchange (OTSI) Apparatus that has relatively low optical fiber requirements and good attenuation and signal-to-noise characteristics. This OTSI uses parallel feedback (PFB) to provide the delays. This PFB OTSI can be implemented with an n.times.n optical crossbar switch. The PFB OTSI is conditionally, i.e., rearrangeably, non-blocking for 16.times.16 crossbar switch implementations if a controller using the control method of the invention is also included.
Claims16
An OTSI for interchanging at least one time slot of data of a plurality of time slots, comprising:
- a n.times.n optical switch, where n is an integer greater than 2;
- an input optical fiber connected to a first of the n inputs of the n.times.n optical switch;
- an output fiber connected to a first of the n outputs of the n.times.n optical switch;
- a plurality of up to n-1 optical delay fibers, each of the optical fibers having one end connected to an output of the remaining n-1 outputs of the n.times.n optical switch and a second end connected to a respective input of remaining n-1 inputs of the optical switch;
- and
- means for controlling said optical switch so that a given time slot is routed from said first input through at least one of the delay fibers and out to said first output.
A method for routing each slot of a frame through an n.times.n parallel feedback OTSI having n-1 of the n outputs connected back through respective delay fibers to n-1 of the n inputs with at least two of the slots being permuted, comprising the steps of:
- determining a delay for each input time slot, respectively by subtracting Mod N a starting position of each time slot from a final position of each time slot
- separating each respective delay into an elemental set of fiber delays required to provide the respective delay
- assigning each elemental delay of each signal to a fiber delay line on a given time slot such that no two signals can enter the same delay fiber during the same time slot.
Dependencies are inferred from the claim text.