Wavelength selective optical routers

The method of adding and dropping signals of selected wavelength bands to and from a main transmission line for optical signals comprising the steps of:

• propagating add/drop wavelength bands along a separate path other than the main transmission line;
• establishing first wavelength band selective loops at serial positions along the main transmission line to return signals in the loop to the line if not diverted;
• establishing second wavelength band selective loops at serial positions along the add/drop path to return signals in the loop to the path if not diverted;
• and
• diverting signals from one or more selected wavelengths of the first loops to corresponding wavelength ones of the second loops to add and/or drop wavelength bands to or from the main transmission line.

A programmable router for optical waveguide systems comprising:

• a first optical waveguide line having add and drop terminals for propagating signals of different wavelengths to be controllably routed;
• a second optical waveguide line for propagating selectively combined ones of the signals at different wavelengths;
• a plurality of optical waveguide shunting units disposed in parallel between the first and second optical waveguide lines, each of the shunting units including a controllable crossover switch and a pair of wavelength selective optical filters, each filter of a different pair of the optical waveguide lines being in a different line and the filters of each pair each being responsive to a chosen wavelength, and
• a routing control system for operating the crossover switches to selectively add and drop wavelengths at the different units.

A programmable, wavelength selective router which directs a programmable combination of wavelength channels between optical waveguides, comprising:

• a first optical waveguide;
• a second optical waveguide;
• a first plurality of grating assisted mode couplers characterized by different add/drop wavelengths, each having an input, throughput, add and drop port, the input and throughput ports of said first plurality of grating assisted mode couplers being disposed in serial fashion along said first optical waveguide;
• a second plurality of grating assisted mode couplers characterized by different add/drop wavelengths, each having an input, throughput, add and drop port, the input and throughput ports of said second plurality of grating assisted mode couplers being disposed in serial fashion along said second optical waveguide;
• a plurality of crossover optical switches, each having a first and second input and a first and second output,
• wherein the drop ports of the first plurality of grating assisted mode couplers are individually coupled to the first switch inputs, the add ports of the first plurality of grating assisted mode couplers are individually coupled to the second switch inputs, the drop ports of the second plurality of grating assisted mode couplers are individually coupled to the second switch outputs and the add ports of the second plurality of grating assisted mode couplers are individually coupled to the first switch outputs.

A router for optical signals comprising:

• a main optical fiber;
• an add/drop optical filter in parallel with the main optical fiber, optical wavelength signals with different wavelengths being propagated in opposite directions on the two fibers;
• and
• a plurality of cross-switching units serially interconnecting the two fibers, each responsive to a selected wavelength and propagating other wavelengths along the two fibers, each cross-switching unit being coupled to controllably change the wavelengths propagated on the main fiber by adding selected wavelength signals from and dropping selected wavelength signals to the add/drop optical fiber.

A signal switching unit for selectively directing signals at optical wavelengths from a first optical wave transmission line to a second wave transmission line comprising:

• an optical switch having two terminal pairs and selectively controllable to pass signals through from one terminal of a pair to one terminal of the other pair, or alternatively between terminals of the same pair;
• first and second reflective optical signal couplers, each having two pairs of terminals and each reflecting a selected wavelength band received at one terminal of a pair to the other terminal of the pair, and passing other wavelengths through to a terminal of the other pair, each of the couplers being interspersed in a different one of the wave transmission lines at a first set of pass-through terminals, the couplers being bidirectional and the selected wavelength bands being alike, and
• first and second signal loops, each interconnecting one pass-through terminal set of the optical switch to a pass-through set of a different coupler,
• whereby on operation of the switch a selected wavelength band on one of the wave transmission lines can be directed to the other of the wave transmission lines.