Micro-optic delay element for use in a time-division multiplexed system

A circuit for receiving two streams of modulated data and for polarization and time-division multiplexing the two streams onto a single waveguide, comprising:

• a light source for providing a primary signal;
• a first and a second modulator for independently, and in parallel, modulating portions of the primary signal, the first and second modulators for providing two data streams;
• means for operating on at least one of the two data streams and for providing different polarization states between the two data streams;
• and,
• a birefringent crystal having at least two input ports at an end thereof disposed to receive substantially unguided collimated light from first and second modulators, said unguided collimated light being in the form of two modulated data streams having different polarization states, the birefringent crystal having an output port disposed at an opposite end thereof to receive and combine the two modulated data streams into a single time-interleaved data stream, the birefringent crystal being optically coupled with the modulators in the absence of optical fiber therebetween, the birefringent crystal being of suitable shape and dimensions to provide a required optical path length difference between the two modulated data streams passing therethrough to time multiplex the two data steams into the single data stream whereby birefringent crystal has both a combining function and a time delay function.

A method of multiplexing optical signals onto an output port, comprising the steps of:

• providing two modulated polarized optical signals having a polarization difference between the two modulated signals of substantially 90 degrees;
• passing one of the two modulated signals along a first path in a birefringent crystal;
• and
• passing another of the two modulated signals along a second path intersecting the first path at the output port of the birefringent crystal, whereby the modulated signals are combined,
• wherein the modulated signals are passed to the birefringent crystal in the absence of optical fiber, and
• wherein the first path and the second path are of different length, whereby the birefringent crystal combines the two modulated signals into a single time-interleaved data stream.

A circuit for receiving two orthogonally polarized streams of data and for polarization and time-division multiplexing the two streams onto a single waveguide, comprising:

• polarization dependent means having:
• first and second input ports at an end thereof;
• an output port optically coupled with the first and second ports;
• a first unguided optical path and a second unguided optical path disposed between the first and second input ports respectively and the output port, for receiving the two orthogonally polarized data streams and for carrying said data streams to said output port in an unguided manner, the first and second unguided paths being of a different optical path length which differ by an optical path length DnL,
• wherein the length dnL, is selected to provide a required relative time delay between the two data streams as they pass along the first and second unguided paths from the first and second input ports to the output port such that the data streams become a single time-interleaved data stream having a predetermined bit period Dt.