OPTICAL-QUALITY COVER FOR USE WITH AN OPTICAL COUPLING SYSTEM, AND AN OPTICAL COMMUNICATIONS MODULE THAT INCORPORATES THE OPTICAL-QUALITY COVER
In an optical communications module, an optical-quality (O-Q) cover is provided for use with an optical coupling system for protecting a diffractive grating of the optical coupling system from environmental contamination. In accordance with illustrative embodiments, the O-Q cover is used with an optical coupling system that includes a unitary, or integrally-formed, optical body having lenses formed on its lower end and a diffractive grating formed on its upper end. The O-Q cover is disposed in proximity to the diffractive grating and is mechanically coupled to the optical coupling system in a way that seals the portion of the optical coupling system comprising the diffractive grating in order to protect the diffractive grating from environmental contamination.
1 . An optical communications module comprising:
a holder for holding an optical coupling system, the holder having an upper surface in which a recessed area has been formed, the recessed area having an opening formed therein that defines a ledge;
an optical coupling system secured to the holder beneath the opening, the optical coupling system being transparent to light of an operating wavelength, the optical coupling system having at least an upper surface, a lower surface, and side walls, wherein a diffractive grating is formed in the upper surface of the optical coupling system;
at least one optoelectronic component disposed beneath the optical coupling system; and
an optical-quality (O-Q) cover secured to an upper surface of the ledge such that the cover covers the opening formed in the recessed area of the holder, the cover being transparent to light of an operating wavelength, the diffractive grating being spaced apart from the lower surface of the cover by a predetermined distance, D, wherein the cover protects the diffractive grating from contaminants in an environment external to the optical communications module.
2 . The optical communications module of claim 1 , wherein the O-Q cover has upper and lower surfaces that are parallel to one another, the upper and lower surfaces of the cover being smooth and flat in an optical window portion of the cover.
3 . The optical communications module of claim 2 , wherein the side walls of the optical coupling system are in contact with respective inner side walls of the holder, and wherein an adhesive material is disposed in between the side walls of the optical coupling system and the respective inner side walls of the holder, and wherein the adhesive material secures the optical coupling system to the holder.
4 . The optical communications module of claim 3 , wherein an adhesive material is disposed in between the upper surface of the ledge and the lower surface of the cover, and wherein the adhesive material secures the cover to the holder.
5 . The optical communications module of claim 4 , wherein a hermetically-sealed compartment is formed by securing the side walls of the optical coupling system to the respective inner side walls of the holder with the adhesive material and by securing the upper surface of the ledge to the lower surface of the cover with the adhesive material, and wherein the diffractive grating is disposed within the hermetically-sealed compartment.
6 . The optical communications module of claim 2 , wherein the cover is made of a plastic material.
7 . The optical communications module of claim 6 , wherein the plastic material is polyetherimide.
8 . The optical communications module of claim 7 , wherein the cover has a thickness that is selected to ensure that the cover does not bend to an extent that causes the cover to have a lens effect on light of the operating wavelength passing through the cover.
9 . The optical communications module of claim 8 , wherein the thickness is in a range of from about 0.1 millimeters (mm) to about 0.5 mm.
10 . The optical communications module of claim 2 , wherein the cover is made of glass.
11 . The optical communications module of claim 2 , wherein the optical coupling system is a unitary part, the unitary part having one or more lenses formed on the lower surface of the body opposite the diffractive grating formed on the upper surface of the optical coupling system.
12 . The optical communications module of claim 11 , the optical coupling system is made of a plastic material.
13 . The optical communications of claim 12 , wherein the plastic material is polyetherimide.
14 . The optical communications module of claim 11 , wherein at least one of the lenses is a collimating lens and at least one of the lenses is a focusing lens.
15 . The optical communications module of claim 14 , wherein the optical communications module is a parallel optical communications module, and wherein the module comprises a plurality of optoelectronic components.
16 . The optical communications module of claim 15 , wherein the parallel optical communications module is a parallel optical transmitter module, and wherein the plurality of optoelectronic components include a plurality of laser diodes.
17 . The optical communications module of claim 16 , wherein the plurality of optoelectronic components include a plurality of monitor photodiodes, and wherein a plurality of the lenses are collimating lenses and a plurality of the lenses are focusing lenses, and wherein the collimating lenses collimate respective light beams produced by the respective laser diodes and direct the collimated light beams onto the diffractive grating, and wherein the focusing lenses receive respective reflected portions of the collimated light beams directed onto the diffractive grating and focus the respective reflected portions of the collimated light beams onto the respective monitor photodiodes.
18 . The optical communications module of claim 17 , wherein the diffractive grating divides each collimated light beam directed thereon into at least first and second collimated light beams, the first collimated light beam being transmitted through the diffractive grating and through the cover, the second collimated light beams corresponding to the respective reflected portions that are focused by the respective focusing lenses onto the respective monitor photodiodes.
19 . The optical communications module of claim 2 , wherein the parallel optical communications module is a parallel optical receiver module, and wherein the plurality of optoelectronic components include a plurality of photodiodes.
20 . The optical communications module of claim 2 , wherein the parallel optical communications module is a parallel optical transceiver module, and wherein the plurality of optoelectronic components include a plurality of laser diodes and a plurality of photodiodes.