Time-slot interchanger for time division multiplex system utilizing organ arrays of optical fibers

Claim 2

In a time division multiplex communication system in which information is carried in the form of signal pulses in a plurality j of time-wise sequential time slots or words on an input signal path, apparatus for permuting said words to produce a predetermined sequence of said words on an output signal path, comprising: generating means for producing from each of said signal pulses a plurality of at least (2j - 1) optical sub-pulses each propagating along spatially separate paths, a plurality of at least (2j - 1) optical gates each disposed to receive a separate one of said sub-pulses, said gates being normally in an off-state which inhibits transmission of said sub-pulses therethrough, an array of at least (2j - 1) optical fibers cut to different lengths so that the difference in length between functionally adjacent fibers is uniform, one end of each of said fibers being terminated in an input plane and the opposite end of each of said fibers being terminated in an output plane, each of said one ends of said fibers being in registration with a separate one of said gates, means for combining on said output signal path the optical subpulses emerging from the output plane of said array, and control means for applying to predetermined ones of said gates control signals effective to switch said gates to an on-state for a time period approximately equal to the duration of a time slot, said control signals being applied to said gates so that at prescribed times preselected words are coupled to preselected fibers, thereby to delay the sub-pulses in each of said words by a predetermined amount effective to permute said words and to produce said sequence on said output signal path.

Claim 3

The apparatus of claim 1 wherein: said generating means comprises a laser responsive to said signal pulses for producing optical pulses corresponding thereto, a plurality of at least (2j - 1) beam splitters arranged to receive said optical pulses and produce said sub-pulses by partial reflection therefrom, and lens means disposed to focus said sub-pulses onto the inputs of said optical gates.

Claim 4

The apparatus of claim 2 wherein: said output path is an electrical path; and said combining means comprises photodetection means for receiving optical sub-pulses emerging from the output plane of said array and for converting said optical sub-pulses into electrical sub-pulses at the output of said photodetection.

Claim 5

The apparatus of claim 2 wherein: said output path is an optical path, and said combining means comprises a plurality of reflectors positioned to receive optical sub-pulses emerging from the output plane of said array and oriented to reflect a portion of said sub-pulses collinearly along said output path.

Claim 6

The apparatus of claim 2 wherein: said output path is an optical path, and said combining means includes a relatively large diameter optical fiber to which the outputs of the array fibers, being of relatively smaller diameter, are optically coupled.

Claim 7

The apparatus of claim 1 wherein: said information is in the form of a coded frame of said signal pulses, said frame being of duration ts and containing j words or time slots W1W2...Wj, each of duration tw, and in order to transfer the kth word Wk (0 < or = k < or = j) on said input signal path into the mth time-slot (0 < or = m < or = j) on said output signal path, said control means applies a control signal to the Nth one of said gates (1 < or = N < or = 2j - 1) at a time tg (0 < or = tg < or = ts - tw) given by N j + m - k anD tg (k - 1) tw.

Claim 8

In a time division multiplex communication system, a switching network for transferring the ith word on any one of m input signal paths or buses to the nth time slot on any one of m output signal paths or buses comprising: at least three tandem stages I, II and III each including m apparatuses according to claim 1 arranged in parallel with one another, at least two serial-to-parallel converters, one converter interposed between stages I and II and the other converter between stages II and III, each of said converters comprising a plurality m of rotary switches arranged in parallel, each of said switches having a single input and m outputs, the inputs of said apparatuses of stage I being coupled to separate ones of said m input buses and the outputs of said apparatuses of stage III being coupled to separate ones of said m output buses, the outputs of said apparatus of stages I and II being coupled to the inputs of separate ones of the next succeeding rotary switch and the outputs of each of said rotary switches being coupled to separate ones of the inputs of said apparatuses of the next succeeding stage as follows: each of said rotary switches comprising: a laser responsive to its associated apparatus according to claim 1 for generating optical pulses which are the analog of the permuted words appearing at the output of said apparatus, means for producing from each of said optical pulses a plurality m of optical sub-pulses propagating along spatially separate paths, a plurality m of optical gates normally in an off-state which inhibits the transmission of said optical sub-pulses therethrough, means for focusing said separate paths onto the inputs of separate ones of said gates, the gth (g 1, 2...m) gate of each rotary switch being coupled to the input to the gth apparatus of the next succeeding stage, and means interposed between said gth gate and said gth apparatus for converting the optical output of said gate into its electrical analog, and, control means for opening the optical gates of each rotary switch cyclically so that said ith word on the jth input bus of stage I (j 1, 2...m) is transmitted through the (i + j - 1)th gate of the jth rotary switch to the input of the (i + j - 1)th apparatus of stage II, where (i + j - 1) is an integer, modulo m, the cyclical opening of said gates for successive rotary switches of stage I being successively one word ahead in phase so that the jth bus of stage I is transmitting to the kth apparatus of stage II (k 1, 2...m) if, and only if, the (j + 1)th bus of stage I is transmitting to the (k + 1)th apparatus of stage II, modulo m, so that the ith word of the jth bus of stage I is transferred into the ith time slot at the input of (i + j - 1)th apparatus of stage II, modulo m, stage II being related to stage III in the same manner that stage II is related to stage I so that said ith word is transferred into the nth time slot on said predetermined output of stage III.