Bidirectional optical communications module having an optics system that reduces optical losses and increases tolerance to optical misalignment

Patent metadata

Field	Value
Publication number	US-9323013-B2
Application number	US-201514851013-A
Country	US
Kind code	B2
Filing date	Sep 11, 2015
Priority date	Apr 19, 2013
Publication date	Apr 26, 2016
Grant date	Apr 26, 2016

Abstract

In a bidirectional optical communications module, an optics system is provided having a lens block that uses a single surface for reflecting light into or reflecting light passing out of the end of the optical fiber and a single surface for reflecting light toward a monitor photodetector. No other surfaces in the lens block are used to turn the light path. A filter block of the optics system that is adjacent to the lens block performs wavelength multiplexing and demultiplexing. The filter block reflects light at either its lower or upper surface back toward the lens block. In some embodiments, a portion of light passes through the upper surface of the filter block to provide some attenuation of light being transmitted so that the light is not coupled back into the light source. Because the upper surface of the filter block is the topmost surface of the optics system, the optics system can be very compact while also limiting the number of surfaces that turn the light path. Limiting the number of surfaces in the optics system that turn the light path reduces optical losses and increases tolerance to optical misalignment.

First claim

What is claimed is:

1. A bidirectional (BiDi) optical communications module for communication over a BiDi optical link, the module comprising:
at least a first light source;
at least a first photodetector;
a lens block, the lens block having an optical port for coupling light between at least a first end of a first optical fiber cable and a first surface of the lens block, wherein the first end of the first optical fiber cable is mechanically coupled with the port; and
a filter block spaced apart from the lens block by a gap and optically aligned with the lens block, the filter block having a first filter element disposed on a lower surface thereof and a second filter element disposed on an upper surface thereof, the first filter element being transmissive to light of a first wavelength and reflective to light of a second wavelength, the second filter element being at least partially reflective to light of the second wavelength, wherein a first light beam passing out of the end of the optical fiber is directed by the first surface of the lens block onto the filter block and is reflected by either the first filter element or the second filter element onto the lens block, the lens block coupling the first light beam onto the first photodetector, wherein at least a first portion of a second light beam produced by the first light source is directed by the lens block onto the filter block, is at least partially reflected by either the first filter element or the second filter element onto the lens block, and coupled by the first surface of the lens block into the first end of the first optical fiber cable.

2. The BiDi optical communications module of claim 1 , wherein the first wavelength is an operating wavelength of the first photodetector such that the first light beam is of the first wavelength, and wherein the second wavelength is an operating wavelength of the first light source such that the second light beam is of the second wavelength, and wherein the first light beam passes through the first filter element and is reflected by the second filter element onto the lens block and wherein at least the first portion of the second light beam is reflected by the first filter element onto the lens block.

3. The BiDi optical communications module of claim 2 , further comprising:
at least a second photodetector, and wherein the lens block includes a second surface that reflects a second portion of the second light beam toward the second photodetector, the lens block coupling the second portion of the second light beam onto the second photodetector, the second photodetector being used to monitor a power level of the second light beam produced by the first light source.

4. The BiDi optical communications module of claim 3 , wherein the lens block further comprises:
first, second and third lenses formed in or secured to the lens block, the first lens coupling the first light beam reflected by the second filter element onto the first photodetector, the second lens coupling the second light beam produced by the first light source onto the second surface of the lens block, the third lens coupling the second portion of the second light beam onto the second photodetector.

5. The BiDi optical communications module of claim 4 , wherein the lens block further comprises:
a fourth lens formed in or secured to the lens block, the fourth lens coupling the second light beam reflected by the first filter element onto the first surface of the lens block, the fourth lens coupling the first light beam reflected by the first surface of the lens block onto the filter block.

6. The BiDi optical communications module of claim 5 , wherein the first, second and third lenses are aspherical lenses.

7. The BiDi optical communications module of claim 6 , wherein the fourth lens is an aspherical lens.

8. The BiDi optical communications module of claim 6 , wherein the fourth lens is an irregular lens.

9. The BiDi optical communications module of claim 3 , wherein the first surface is a total internal reflection (TIR) lens.

10. The BiDi optical communications module of claim 3 , wherein the first surface is an irregular lens.

11. The BiDi optical communications module of claim 3 , wherein the second surface is partially reflective and partially transmissive to the second light beam due to a refractive index change at an interface of the lens block and the gap, and wherein the partial reflectivity and partial transmissiveness of the second surface results in the second portion of the second light beam being reflected toward the second photodetector.

12. The BiDi optical communications module of claim 1 , wherein the first light source and the first photodetector are mounted on a mounting surface in a common plane, and wherein the upper and lower surfaces of the filter block are parallel to one another and are parallel to the mounting surface.

13. The BiDi optical communications module of claim 1 , wherein the first light source and the first photodetector are mounted on a mounting surface in a common plane, and wherein the upper and lower surfaces of the filter block are parallel to one another and at an acute angle to the mounting surface.

14. The BiDi optical communications module of claim 1 , wherein the first wavelength is an operating wavelength of the first light source such that the second light beam is of the first wavelength, and wherein the second wavelength is an operating wavelength of the first photodetector such that the first light beam is of the second wavelength, and wherein the first light beam is reflected by the first filter element onto the lens block and wherein at least a portion of the second light beam is reflected by the second filter element, passes through the first filter element, is coupled by the lens block onto the first surface, and is reflected by the first surface into the end of the optical fiber cable.

15. The BiDi optical communications module of claim 14 , wherein at least a portion of the second light beam passes through the second filter element.

16. The BiDi optical communications module of claim 14 , further comprising:
at least a second photodetector, and wherein the lens block includes a second surface that reflects a second portion of the second light beam toward the second photodetector, the lens block coupling the second portion of the second light beam onto the second photodetector, the second photodetector being used to monitor a power level of the second light beam produced by the first light source.

17. The BiDi optical communications module of claim 16 , wherein the lens block further comprises:
first, second and third lenses formed in or secured to the lens block, the first lens coupling the first light beam reflected by the first filter element onto the first photodetector, the second lens coupling the second light beam produced by the first light source onto the second surface of the lens block, the third lens coupling the second portion of the second light beam onto the second photodetector.

18. The BiDi optical communications module of claim 17 , wherein the lens block further comprises:
a fourth lens formed in or secured to the lens block, the fourth lens coupling the second light beam reflected by the second filter element onto the first surface of the lens block, the fourth lens coupling the first light beam reflected by the first surface of the lens block onto the filter block.

19. The BiDi optical communications module of claim 18 , wherein the first, second and third lenses are aspherical lenses.

Assignees

• Avago Technologies General Ip

Inventors

• Shao Bing
• Chen Ye
• Chan Seng-Kum

Classifications

• G02B6/32

  having lens focusing means {positioned between opposed fibre ends (with lens being an integral part of the single fibre end G02B6/262)} · CPC title

• G02B6/4246 Primary

  Bidirectionally operating package structures · CPC title

• G02B6/4206

  Optical features (G02B6/4207, G02B6/421 take precedence) · CPC title

• G02B6/4286

  Optical modules with optical power monitoring · CPC title

• G02B17/006

  Systems in which light light is reflected on a plurality of parallel surfaces, e.g. louvre mirrors, total internal reflection [TIR] lenses (Fresnel mirrors G02B5/09, Fresnel lenses G02B3/08) · CPC title