Passively aligned bi-directional optoelectronic transceiver module assembly

Claims

What is claimed is:

1. An assembly (10) for terminating an optical fiber (12) which transmits information bi-directionally, transmission of information in a first direction within the fiber being effected by light at a first wavelength and transmission of information in the second direction within the fiber being effected by light at a second wavelength, the assembly comprising:

a monocrystalline material support member (14) having a major planar surface (16);

a planar monocrystalline material base member (28) secured to said support member major planar surface, said base member being formed with first (30) and second (32) through apertures each having four side walls (34, 36, 38, 40, 42, 44, 46, 48) formed by crystallographic planes of the monocrystalline material which are oblique to said support member major planar surface, said apertures being in the form of truncated pyramids and said base member being oriented so that the truncated pyramids are inverted with the smaller openings of both said apertures adjacent said support member major planar surface;

a first reflective layer (50) disposed on a side wall (40) of said first aperture;

a light source (24) mounted to said support member major planar surface within said first aperture of said base member, said light source being selectively controllable to generate a light beam at said first wavelength directed to said first reflective layer so that said source light beam is reflected by said first reflective layer to exit the larger opening of said first aperture;

a light detector (26) mounted to said support member major planar surface within said second aperture of said base member, said light detector having a light sensitive surface area (52) exposed to a received light beam entering the larger opening of said second aperture, said light detector being responsive to light at said second wavelength impinging on said light sensitive surface area for providing a predetermined electrical signal;

a planar monocrystalline material lid (54) secured to said base member over said first and second apertures, said lid being transparent to light at said first and second wavelengths;

a monocrystalline material cover member (56) having a major planar surface (58) secured to said lid, said cover member having a cavity (60, 62) in its major planar surface capable of receiving an end portion of said optical fiber (12), said cavity having an end face (64) formed by a crystallographic plane of the monocrystalline material which is oblique to said cover member major planar surface;

a second reflective layer (66) disposed on said cover member cavity end face (64); and

a diffractor (68) secured to said lid in the vicinity of said cover member cavity;

wherein said diffractor and said first and second reflective layers are so arranged that:

(a) light at said second wavelength exiting said fiber (12) is reflected by said second reflective layer (66), passes through said diffractor (68) and is directed through said lid (54) to said light sensitive surface area (52) of said light detector (26); and

(b) light at said first wavelength generated by said light source (24) is reflected by said first reflective layer (50), passes through said lid (54) and said diffractor (68), is directed to said second reflective layer and is reflected by said second reflective layer along a path so that it enters said optical fiber (12).

2. The assembly according to claim 1 further including:

means (80) for hermetically sealing said base member to said support member; and

means (82) for hermetically sealing said lid to said base member.

3. The assembly according to claim 1 wherein said diffractor comprises a computer generated hologram.

4. The assembly according to claim 3 wherein said diffractor (68) comprises a radially symmetric computer generated hologram.

5. The assembly according to claim 4 wherein said diffractor comprises two superimposed radially symmetric computer generated holograms, one for each of said first and second wavelengths of light.

6. The assembly according to claim 3 wherein said diffractor comprises a computer generated hologram integrally formed in said lid.

7. The assembly according to claim 3 wherein said diffractor comprises a separately formed computer generated hologram bonded to said lid.

8. The assembly according to claim 1 wherein said support member, said base member, said lid and said cover member are all formed from monocrystalline silicon which is processed by photolithographic wet etching to form the apertures of said base member and the cavity of said cover member.

9. The assembly according to claim 8 wherein the major surfaces of said monocrystalline silicon base member and cover member are in the {100} crystallographic plane of the silicon and the etching exposes a {111} crystallograpic plane of the silicon.

10. The assembly according to claim 1 wherein said base member is formed with a first plurality of alignment detents (70) on its surface facing said lid, said lid is formed with an equal first plurality of alignment detents (72) on its surface facing said base member and a second plurality of alignment detents (74) on its surface facing said cover member, and said cover member is formed with an equal second plurality of alignment detents (76) on its surface facing said lid, the assembly further comprising a first plurality of alignment balls (78) each in a respective pair (70, 72) of alignment detents of said base member and said lid and a second plurality of alignment balls (78) each in a respective pair (74, 76) of alignment detents of said lid and said cover member.

11. The assembly according to claim 1 wherein said apertures (30, 32) of said base member (28) are in side-by-side alignment with each of the side walls of each aperture being parallel to a respective side wall of the other aperture.

12. The assembly according to claim 11 wherein said first reflective layer (50) is disposed on that side wall (40) of said first aperture (30) which is adjacent said second aperture (32).

13. An assembly (10) for terminating an optical fiber (12) which transmits information bi-directionally, transmission of information in a first direction within the fiber being effected by light at a first wavelength and transmission of information in the second direction within the fiber being effected by light at a second wavelength, the assembly comprising:

a monocrystalline material support member (14) having a major planar surface (16);

a planar monocrystalline material base member (28) secured to said support member major planar surface, said base member being formed with a through aperture (30,32), said aperture having an opening remote from said support member major planar surface;

structure secured to said support member major planar surface within said aperture of said base member, said structure having a wall (40) oblique to said support member major planar surface;

a first reflective layer (50) disposed on said wall (40) of said structure;

a light source (24) mounted to said support member major planar surface within said aperture of said base member, said light source being selectively controllable to generate a light beam at said first wavelength directed to said first reflective layer so that said source light beam is reflected by said first reflective layer to exit the remote opening of said aperture;

a light detector (26) mounted to said support member major planar surface within said aperture of said base member, said light detector having a light sensitive surface area (52) exposed to a received light beam entering the remote opening of said aperture, said light detector being responsive to light at said second wavelength impinging on said light sensitive surface area for providing a predetermined electrical signal;

a planar monocrystalline material lid (54) secured to said base member over said aperture, said lid being transparent to light at said first and second wavelengths;

a monocrystalline material cover member (56) having a major planar surface (58) secured to said lid, said cover member having a cavity (60, 62) in its major planar surface capable of receiving an end portion of said optical fiber (12), said cavity having an end face (64) formed by a crystallographic plane of the monocrystalline material which is oblique to said cover member major planar surface;

a second reflective layer (66) disposed on said cover member cavity end face (64); and

a diffractor (68) secured to said lid in the vicinity of said cover member cavity;

wherein said diffractor and said first and second reflective layers are so arranged that:

(a) light at said second wavelength exiting said fiber (12) is reflected by said second reflective layer (66), passes through said diffractor (68) and is directed through said lid (54) to said light sensitive surface area (52) of said light detector (26); and

(b) light at said first wavelength generated by said light source (24) is reflected by said first reflective layer (50), passes through said lid (54) and said diffractor (68), is directed to said second reflective layer and is reflected by said second reflective layer along a path so that it enters said optical fiber (12).

14. The assembly according to claim 13 wherein said base member aperture includes a pair of apertures (30,32) each in the form of an inverted truncated pyramid, said pair of apertures being side-by-side so that said structure is formed by base member material separating said pair of apertures, said light source being within a first (30) of said apertures and said light detector being within a second (32) of said apertures, and said wall (40) being a side wall of said first aperture.

15. A Passively Aligned Bi-directional Optoelectronic Module, comprising:

a. A support member having a top surface and a bottom surface, said support member having disposed on said top surface a light source and a light detector as well as a base member having a top surface and a bottom surface, said base member having at least one aperture selectively etched from said top surface to said bottom surface, said apertures having sidewalls at well defined angles, at least one of said sidewalls of said at least one aperture having a reflecting surface disposed thereon; and

b. A optically transparent lid having a top surface and a bottom surface, said lid disposed on said top surface of said base member, said lid having disposed on said top surface of said lid a diffractor for wavelength separation and a cover member, said cover member having a selectively v-shaped groove having a first end and a second, said second end terminating into a selectively etched cavity, said cavity having an endface, said endface having a reflective surface disposed thereon, and said v-shaped groove having an optical fiber disposed therein, whereby light transmitted to and from said optical fiber is reflected from said endface of said cavity, is diffracted by said diffractor, is transmitted through said lid, is impingent on said reflective surface of said at least one wall of said sidewalls of said at least one aperture having a reflective surface disposed thereon to said detector and from said light source.

16. A Passively Aligned Bi-Directional Optoelectronic Module as recited in claim 15, wherein said diffractor is a hologram.

17. A Passively Aligned Bi-Directional Optoelectronic Module as recited in claim 15, wherein said support member, said base member and said cover member are made of monocrystalline material and said groove, said cavity and said at least one aperture are formed by etching said monocrystalline material to expose well defined crystalline planes.

18. A Passively Aligned Bi-Directional Optoelectronic Module as recited in claim 15, wherein said lid, said cover member and said base member have selectively disposed alignment detents for receiving alignment balls therein, whereby the elements of the Module are passively aligned.

19. A Passively Aligned Bi-Directional Optoelectronic Module as recited in claim 17, wherein said support member, said base member said lid and said cover member are made of monocrystalline material having respective major surfaces in the (100) crystalline plane and said groove, said cavity and said at least one aperture are formed by etching said monocrystalline material to expose crystalline planes in the (110) crystalline planes.

20. A Passively Aligned Bi-Directional Optoelectronic Module as recited in claim 15, wherein said optical fiber supports an optical signal of first and second wavelength, said first wavelength being emitted from said light source and said second wavelength being detected by said light detector.

BACKGROUND OF THE INVENTION

This invention relates to optical transmission and, more particularly, to an optoelectronic transceiver module assembly for terminating a bi-directional optical fiber.

Packages for optoelectronic devices terminating optical fibers and utilizing silicon processing technology are known, as exemplified by U.S. Pat. No. 4,897,711 to Blonder et al. The '711 patent discloses a subassembly for use in packaging an optoelectronic device (e.g., LED or photodiode) which includes a silicon base and lid having a variety of etched features (e.g., grooves, cavities, alignment detents) and metalization patterns (e.g., contacts, reflectors) which enable the device to be mounted on the base and coupled to the fiber. Specifically, a subassembly according to the Blonder et al patent is for use with unidirectional transmission over the optical fiber. It would be desirable to have such a package which can be utilized in a bi-directional transmission system.

It is therefore a primary object of the present invention to provide an assembly for terminating an optical fiber which transmits information bi-directionally.

It is a further object of this invention to provide such an assembly which is manufactured by utilizing silicon processing techniques to keep the cost low, the package small and the tolerances precise.

It is yet another object of this invention to achieve high precision small packages for such an assembly which are thermally stable and allow batch processing to achieve low cost.

SUMMARY OF THE INVENTION

The foregoing, and additional, objects of this invention are attained by providing an assembly for terminating an optical fiber which transmits information bi-directionally, transmission of information in a first direction within the fiber being effected by light at a first wavelength and transmission of information in a second direction within the fiber being effected by light at a second wavelength. The assembly comprises a monocrystalline material support member having a major planar surface and a planar monocrystalline material base member secured to the support member major planar surface. The base member is formed with first and second through apertures each having four side walls formed by crystallographic planes of the monocrystalline material oblique to the support member major planar surface. The apertures are in the form of truncated pyramids and the base member is oriented so that the truncated pyramids are inverted, with the smaller openings of both the apertures being adjacent the support member major planar surface. A first reflective layer is disposed on a side wall of the first aperture and a light source is mounted to the support member major planar surface within the first aperture of the base member, the light source being selectively controllable to generate a light beam at the first wavelength directed to the first reflective layer so that the light beam is reflected to exit the larger opening of the first aperture. A light detector is mounted to the support member major planar surface within the second aperture of the base member and has a light sensitive surface area exposed to a received light beam entering the larger opening of the second aperture. The light detector is responsive to light at the second wavelength impinging on the light sensitive surface area for providing a predetermined electrical signal. A planar monocrystalline material lid is secured to the base member over the first and second apertures, the lid being transparent to light at the first and second wavelengths. A monocrystalline material cover member having a major planar surface is secured to the lid, the cover member having a cavity in its major planar surface capable of receiving an end portion of the optical fiber. The cavity has an end face formed by a crystallographic plane of the monocrystalline material which is oblique to the cover member major planar surface and a second reflective layer is disposed on that end face. Further, a diffractor is secured to the lid in the vicinity of the cover member cavity. The diffractor and the first and second reflective layers are so arranged that light exiting the fiber is reflected by the second reflective layer, passes through the diffractor and is directed through the lid to the light sensitive surface area of the light detector. At the same time, light generated by the light source is reflected by the first reflective layer, passes through the lid and the diffractor, is directed to the second reflective layer and is reflected by the second reflective layer along a path so that it enters the optical fiber.

In accordance with an aspect of this invention, the assembly further includes means for hermetically sealing the base member to the support member and means for hermetically sealing the lid to the base member.

In accordance with another aspect of this invention, the diffractor comprises a computer generated hologram. More specifically, the diffractor comprises two superimposed radially symmetric computer generated holograms, one for each of the first and second wavelengths of light.

In accordance with yet another aspect of this invention, the diffractor comprises a radially symmetric computer generated hologram formed in the lid.

In accordance with a further aspect of this invention, the support member, the base member, the lid and the cover member are all formed from monocrystalline silicon which is processed by photolithographic etching to form the apertures of the base member and the cavity of the cover member.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing will be more readily apparent upon reading the following description in conjunction with the drawings in which like elements in different figures thereof are identified by the same reference numeral and wherein:

FIG. 1 is a cross sectional view schematically illustrating an assembly constructed in accordance with the principles of this invention;

FIG. 2 is a top plan view of the base member taken along the line 2--2 in FIG. 1; and

FIG. 3 is a bottom plan view of the cover member taken along the line 3--3 in FIG. 1.

DETAILED DESCRIPTION

When utilizing single mode optical fibers, precision tolerances for the optoelectronic interface are required because of the small numerical aperture of the fiber. Thus, all such interface packages must be precisely aligned. It is advantageous that such alignment be "passive", rather than "active", active alignment being where the optoelectronic devices are operating during the alignment process. Using silicon processing techniques, packages which are passively aligned have been developed, as disclosed for example in the aforereferenced Blonder et al patent. The package illustrated in FIGS. 1-3 herein provides such passive alignment for a bi-directionally transmitting optical fiber. With such bi-directional transmission, transmission of information in a first direction within the optical fiber is effected by light at a first wavelength (e.g., 1.3 .mu.m) and transmission of information in a second direction within the optical fiber is effected by light at a second wavelength (e.g., 1.55 .mu.m).

As shown in FIG. 1, the inventive package, designated generally by the reference numeral 10, terminates an optical fiber 12. All of the major parts of the package 10 are formed of monocrystalline silicon, precisely machined in a known manner either by photolithographic wet etching or by reactive ion etching. The package 10 includes a support member 14 formed from a silicon wafer board (sometimes referred to as a silicon bench). The support member 14 has a major planar surface 16 on which are disposed recessed conductive traces 18. Wire bond pads 20 in electrical contact with the conductive traces 18 are provided for interconnection with external circuitry. Formed on the surface 16 are alignment pedestals 22 and standoffs (not shown). The alignment pedestals 22 and the standoffs are produced by utilizing reactive ion etching to remove parts of the surface 16 so as to provide vertical walls for the pedestals and standoffs. The pedestals 22 and the standoffs are for the purpose of aligning the optoelectronic devices 24, 26 mounted to the surface 16, as is known in the art.

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