Multiple-wavelength optical transceiver

#This invention relates to optical transceivers and, more particularly, to a multiple-wavelength optical transceiver and a packaging arrangement therefore.

#The goal in local fiber access is to provide high bandwidth two-way communications to the home. Any practical local fiber access network requires a transceiver which is compact, rugged and, most of all, cheap. One network transmission design uses a high-bandwidth analog broadcast optical signal at 1.5 .mu.m, with two way time-multiplexed communications using a 1.3 .mu.m optical signal carried on the same fiber.

#At first glance, fiber optic systems which use free space propagation and bulk optical components seem to be obsolete. They could be replaced by integrated optic arrangements which eliminate the large number of expensive alignments. Yet bulk optic arrangements are often still the most cost-effective approach. The basic idea of this standard approach is shown in FIG. 1.

#In the drawing,

#FIG. 1 shows an illustrative block diagram of a prior art bulk optic transceiver for providing bidirectional communications,

#FIG. 2a shows an illustrative diagram of a transceiver in accordance with the present invention and FIG. 2b shows the resulting diffraction patterns for illustrative 1.3 and 1.55 .mu.m optical signals passing through the color-selective grating used in the transceiver of FIG. 2a,

#In the following description, each item or block of each figure has a reference designation associated therewith, the first number of which refers to the figure in which that item is first located (e.g., 210 is located in FIG. 2).

#Before we discuss specific embodiments, the present invention is generally directed to optical demultiplexing apparatus capable of spatially separating a multiplexed optical signal into two or more optical wavelength signals thereof. An input multiplexed optical signal present on a first plane is imaged through a color-selective grating to a second plane. The color-selective grating has a nonlinear change of diffraction characteristics as a function of incident wavelength to provide substantial spatial separation in the second plane between bands of wavelengths proximate to the two or more optical wavelength signals. In another demultiplexing embodiment, the apparatus may use a polarization-selective grating to spatially separate a polarization-multiplexed optical signal into two substantial spatially separated optical polarization signals. In other embodiments, the optical apparatus may be used as an optical signal multiplexer, splitter, or combiner. Operation of these different apparatuses is best understood with reference to specific implementations described in the following paragraphs.

#Shown in FIG. 2a is an illustrative diagram of a 2-wavelength demultiplexing transceiver for imaging an input multiplexed optical signal present on a first plane through a color-selective grating to a second plane. FIG. 2b shows a longitudinal bisection view of the resulting diffracted beam paths for illustrative 1.3 and 1.55 .mu.m optical signals passing through the color-selective grating used in the transceiver of FIG. 2a. As will be discussed our 2-wavelength fiber transceiver of FIG. 2a is simple and compact, and needs only a single lateral alignment for all three devices: the 1.3 um detector, 1.3 um transmitter, and 1.5 um detector or receiver. All other alignments are lithographically controlled.