Micro-optic delay element for use in a polarization 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.

An integrated fiberless optical circuit for receiving two streams of modulated data and for polarization multiplexing the two data streams onto a single waveguide, comprising:

• a modulator for independently, and in parallel, modulating two optical signals, the modulator for providing two modulated data streams;
• means optically coupled with the modulator in a fiberless manner for operating on at least one of the two data streams and for providing different polarization states between the two data streams;
• and,
• a polarization beam splitter/combiner (PBS/C) having at least two input ports optically coupled in a fiberless manner to the modulator and the means for providing different polarization states, an end of the PBS/C disposed to receive the two modulated data streams having different polarization states, the PBS/C having an output port disposed at an opposite end thereof to receive and combine the two modulated data streams into a single time multiplexed data stream, the PBS/C being of suitable 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 in the absence of other delay means, or the PBS/C being of suitable 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 in the presence of a delay means having a refractive index difference of at least 0.5 from that of air.

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.