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Detecting Multiplexed Picosecond Pulses

IP.com Disclosure Number: IPCOM000073734D
Original Publication Date: 1971-Jan-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 3 page(s) / 54K

Publishing Venue

IBM

Related People

Dakss, ML: AUTHOR [+4]

Abstract

A device is provided for detecting multiplexed picosecond optical pulses using integrated optical technology. Strings of encoded picosecond pulses (bits) are coupled into a plurality of separate waveguides, the entire string of pulses being introduced in parallel into each waveguide. A series of check pulses is also coupled into the waveguides, each check pulse being spaced such that each check pulse occurs in a different bit position. If data pulses are present in the bit positions, the combination of the check pulse and the data pulse produces a signal having a unique wavelength that is detected to indicate that a bit is present. If no data bit is present, the check pulse alone will not produce the unique wavelength signal.

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Detecting Multiplexed Picosecond Pulses

A device is provided for detecting multiplexed picosecond optical pulses using integrated optical technology. Strings of encoded picosecond pulses (bits) are coupled into a plurality of separate waveguides, the entire string of pulses being introduced in parallel into each waveguide. A series of check pulses is also coupled into the waveguides, each check pulse being spaced such that each check pulse occurs in a different bit position. If data pulses are present in the bit positions, the combination of the check pulse and the data pulse produces a signal having a unique wavelength that is detected to indicate that a bit is present. If no data bit is present, the check pulse alone will not produce the unique wavelength signal.

The pulses are spaced by an amount of time t(s), and are of width t(w) (approx. psec). The mode locking repetition period is t(s) << t(o) = 2L/C. Time t(s) should be made to approach t(w) for maximum multiplexing.

Modulation corresponds to pulses being either "there" or "not there." The t(o)/t(s) time intervals contained within each time period t(o) are considered separate channels. The channels are to be separated or demultiplexed, and a determination made whether a pulse is "there" or "not there" during every time period t(o).

Optical waveguides 1 and 1a-1g, for example glass films, are formed on a substrate 2. Check pulses at a spacing t(o) are introduced into waveguide 1 from a mode-locked laser via a check pulse coupler 3, such as a grating coupler.

Couplers 4a-4g, for example grating couplers, couple signals in parallel into all waveguides 1a-1g. The signals, for example, in sets of seven labeled a-g, enter the waveguides in a time position to produce arrays of pulses propagating as represented by the triangles. The dotted outlines represent the absence of a signal.

The check pulses in waveguide 1 represented by circles, are so delayed that the one in channel la will coincide, after the signal coupler 4a, with the signal pulse in the A position in the string, that in channel 1b will coincide...