Optical module and method for assembling the same

• US 20030026540A1
• Filed: 08/05/2002
• Published: 02/06/2003
• Est. Priority Date: 08/06/2001
• Status: Active Grant

• Current Assignee: Go!Foton Holdings, Inc.
• Original Assignee: Nippon Sheet Glass Company Limited (Nippon Telegraph and Telephone Corporation)
• Inventors: Ohyama, Ikuto, Tanaka, Hiroyuki, Ishimaru, Takeshi, Taniyama, Minoru, Fukuzawa, Takashi, Kittaka, Shigeo
• Granted Patent: US 6,782,162 B2
• Time in Patent Office: Days
• US Class Current: 385/34
• CPC Class Codes: G02B 6/2937 In line lens-filtering-lens devices, i.e. elements arranged along a line and mountable in a cylindrical package for compactness, e.g. 3- port device with GRIN lenses sandwiching a single filter operating at normal incidence in a tubular package
• CPC Class Codes: G02B 6/32 having lens focusing means positioned between opposed fibre ends with lens being an integral part of the single fibre end G02B6/262

Abstract

An optical module which satisfies a required insertion loss and can be easily assembled with high productivity. The optical module includes first optical fiber, a first lens, an optical device, a second lens, and second optical fiber. The first lens receives an incident light from the first optical fiber and converts the incident light into a parallel light. The optical device receives the parallel light and performs predetermined optical processing on the parallel light. The second lens receives a transmitted parallel light from the optical device and converge the transmitted parallel light to produce an outgoing light. The second optical fiber receives the outgoing light. An optical axis of the first lens and an optical axis of the second lens are substantially coincident with each other. An optical axis of the first optical fiber and an optical axis of the second optical fiber are substantially parallel with each other and substantially parallel to the optical axes of the first and the second lenses.

Claims

1. An optical module, comprising:

a first optical fiber;

a first lens, optically coupled with the first optical fiber, for receiving an incident light from the first optical fiber and converting the incident light into a parallel light;

an optical device for receiving the parallel light and performing predetermined optical processing on the parallel light;

a second lens for receiving a transmitted parallel light from the optical device and converging the transmitted parallel light to produce an outgoing light; and

a second optical fiber, optically coupled with the second lens, for receiving the outgoing light;

wherein an optical axis of the first lens and an optical axis of the second lens are substantially coincident with each other, and

an optical axis of the first optical fiber and an optical axis of the second optical fiber are substantially parallel with each other and substantially parallel to the optical axes of the first and the second lenses.

2. The optical module according to claim 1, further comprising:

a third optical fiber, optically coupled with the first lens, and having an axis in parallel with the optical axis of the first optical fiber and separated as much as a predetermined distance; and

wherein the first lens converges the parallel light reflected by the optical device to produce a reflected outgoing light, and provides the reflected outgoing light to the third optical fiber.

3. The optical module according to claim 1, wherein the first lens includes a light emitting surface opposed to the optical device and for emitting the parallel light,

the second lens includes a light receiving surface opposed to the function device and for receiving the transmitted parallel light, and

a distance between a center of the light emitting surface of the first lens and a center of the light receiving surface of the second lens is equal to 1 mm or less.

4. The optical module according to claim 1, wherein each of the first and the second lenses has a lens length larger than the corresponding lens diameter thereof, and

each of the first and the second lenses has a cylindrical periphery whose center axis is parallel to the optical axis of the corresponding lens.

5. The optical module according to claim 1, wherein each of the first and the second lenses is a gradient index rod lens having a refractive index distributed in a radial direction of a circular section perpendicular with respect to the optical axis.

6. The optical module according to claim 1, further comprising, a circular cylinder tube for housing the first and the second lenses so that the axis of the first lens and the axis of the second lens are substantially coincident with each other.

7. The optical module according to claim 1, further comprising, a housing groove having a V-shape cross section and for housing the first lens and the second lens so that the axis of the first lens and the axis of the second lens are substantially coincident with each other.

8. The optical module according to claim 1, further comprising, a first capillary optically coupled with the first lens and for supporting the optical fiber, and a second capillary coupled with the second lens and for supporting the second optical fiber, and

wherein an outside diameter of at least either of the first and the second capillaries is equal to an outside diameter of the corresponding lens.

9. The optical module according to claim 2, wherein the first lens has a focal point with a focal distance f, and

a displacement amount of the optical device from the focal point of the first lens is within ±

25% of the focal distance f of the first lens.

10. The optical module according to claim 2, wherein each of a vertical oblique angle θ

x and a horizontal oblique angle θ

y of the first and the third optical fiber with respect to the optical axis of the first lens is set within 0.2 degrees.

11. The optical module according to claim 2, wherein each of a vertical oblique angle θ

x and a horizontal oblique angle θ

y of the second optical fiber with respect to the optical axis of the second lens is set within 0.2 degrees.

12. The optical module according to claim 2, wherein each of the vertical oblique angle θ

x and the horizontal oblique angle θ

y of the first and the third optical fiber with respect to the optical axis of the first lens is set within 0.2 degrees, and

each of the vertical oblique angle θ

x and the horizontal oblique angle θ

y of the second optical fiber with respect to the optical axis of the second lens is set within 0.2 degrees.

13. The optical module according to claim 2, wherein each of the first lens and the second lens has a focal point with the focal distance f, and

a distance between the first lens and the second lens is within a range of 2f±

2f/4.

14. The optical module according to claim 2, wherein each of the vertical oblique angle θ

x and the horizontal oblique angle θ

y of the first and the third optical fiber with respect to the optical axis of the first lens is set within 0.2 degrees,

each of a vertical oblique angle θ

x and a horizontal oblique angle θ

y of the second optical fiber with respect to the optical axis of the second lens is set within 0.2 degrees respectively,

each of the first lens and the second lens has a focal point with the focal distance f, and

a distance between the first lens and the second lens is within a range of 2f±

2f/4.

15. The optical module according to claim 14,wherein a displacement between the optical axis of the first lens and the optical axis of the second lens is set within 2.5% of the focal distance f.

16. The optical module according to claim 2, wherein each of the vertical oblique angle θ

x and the horizontal oblique angle θ

y of the first and the third optical fiber with respect to the optical axis of the first lens is set within 0.2 degrees,

each of the vertical oblique angle θ

x and the horizontal oblique angle θ

y of the second optical fiber with respect to the optical axis of the second lens is set within 0.2 degrees,

each of the first lens and the second lens has the focal point with the focal distance f, and

a displacement between the optical axis of the first lens and the optical axis of the second lens is set within 2.5% of the focal distance f.

17. The optical module according to claim 2, wherein the first lens includes a first oblique plane which inclines with respect to the optical axis of the first lens and is optically coupled with the first optical fiber,

the second lens includes a second oblique plane which inclines with respect to the optical axis of the second lens and is optically coupled with the second optical fiber,

a relative rotational displacement angle θ

z of the first and the second oblique planes is defined about the optical axes of the first and the second lenses as an rotation axis, and

the relative rotational displacement angle θ

z of the first and the second oblique planes is set within 20 degrees.

18. The optical module according to claim 2, wherein a vertical inclination of the first lens with respect to the optical axis of the first lens is set within 1.5 degrees, and a vertical inclination of the second lens with respect to the optical axis of the second lens is set within 1.5 degrees.

19. The optical module according to claim 18, wherein the first lens has a light emitting end face opposed to the second lens for emitting the parallel light,

the second lens has a light receiving end face opposed to the first lens for receiving the parallel light,

each of the vertical oblique angle θ

x and the horizontal oblique angle θ

y of the emitting end face of the first optical lens with respect to the optical axis of the first lens is set within 10 degrees, and

each of the vertical oblique angle θ

x and the horizontal oblique angle θ

y of the incident end face of the second lens with respect to the optical axis of the second lens is set within 10 degrees.

20. The optical module according to claim 19, wherein the first lens includes a first coupling end face with which the first optical fiber is optically coupled,

the second lens includes a second coupling end face with which the second optical fiber is optically coupled,

each of the vertical oblique angle θ

x and the horizontal oblique angle θ

y of the coupling end face of the first lens with respect to the optical axis of the first lens is set within 2.5 degrees, and

each of the vertical oblique angle θ

x and the horizontal oblique angle θ

y of the coupling end face of the second lens with respect to the optical axis of the second lens is set within 2.5 degrees.

21. A method for assembling an optical module, the optical module comprising:

a first optical fiber;

a first lens, optically coupled with the first optical fiber, for receiving an incident light from the first optical fiber and converting the incident light into a parallel light;

an optical device for receiving the parallel light and performing predetermined optical processing on the parallel light;

a second lens for receiving a transmitted parallel light from the optical device and converging the transmitted parallel light to produce an outgoing light; and

a second optical fiber, optically coupled with the second lens, for receiving the outgoing light;

the method comprising the steps of;

making an optical axis of the first lens and an optical axis of the second lens coincide with each other;

securing the optical device to a predetermined position between the first and the second lenses;

securing the first and the second lenses so that a distance between a center of a light emitting face of the first lens and a center of a light receiving face of the second lens opposed to the first lens becomes a predetermined value;

arranging the first and the second optical fibers in parallel with optical axes of the first and the second lenses;

introducing a light having a predetermined wavelength and transmitting through the optical device into the first lens from the first optical fiber;

adjusting at least either of a relative position between the first optical fiber and the first lens and a relative position between the second optical fiber and the second lens in the same direction as an optical axis of the lens and in two directions perpendicular to the optical axis thereof so that a light amount which enters the second optical fiber becomes larger than a predetermined value; and

securing a whole optical module by keeping the adjusted conditions.

23. The method for assembling an optical module according to claim 21, wherein the step for securing the lens is securing the first and the second lenses so that a predetermined value of a distance between a center of a light emitting face of the first lens and a center of a light receiving surface of the second lens opposed to the first lens is 1 mm or less.

22. A method for assembling an optical module, the optical module comprising:

a first optical fiber;

a first lens, optically coupled with the first optical fiber, for receiving an incident light from the first optical fiber and converting the incident light into a parallel light;

an optical device, for receiving the parallel light and performing predetermined optical processing on the parallel light;

a third optical fiber, optically coupled with the first lens, and having an axis in parallel with the optical axis of the first optical fiber and separated as much as a predetermined distance;

a second lens, for receiving a transmitted parallel light from the optical device and converging the transmitted parallel light to produce an outgoing light; and

a second optical fiber, optically coupled with the second lens, for receiving the outgoing light;

wherein the first lens converges the parallel light reflected by the optical device, produces a reflected outgoing light, and provides the reflected outgoing light to the third optical fiber, the method comprising the steps of;

making an optical axis of a first lens and an optical axis of a second lens substantially coincident with each other;

securing the optical device to a predetermined position between the first and the second lenses;

securing the first and the second lenses so that a distance between a center of a light emitting face of the first lens and a center of a light receiving surface of the second lens opposed to the first lens becomes a predetermined value;

arranging the first and the second optical fibers in parallel with optical axes of the first and the second lenses;

introducing a light having a predetermined wavelength reflected by the optical device and a light having a predetermined wavelength transmitting through the optical device separately or concurrently into the first lens from the first optical fiber;

adjusting a relative position between the first optical fiber and the first lens in the same direction as an optical axis of the lens and in two directions perpendicular to the optical axis thereof so that a light amount which enters the third optical fiber becomes larger than a predetermined value;

adjusting a relative position between the second optical fiber and the second lens in the same direction as an optical axis of the lens and in two vertical directions to the optical axis thereof so that a light amount which enters the second optical fiber becomes larger than a predetermined value; and

securing a whole optical module keeping the adjusted conditions.

24. A method for assembling an optical module, the optical module comprising:

a first optical fiber;

a first lens, optically coupled with the first optical fiber, for receiving an incident light from the first optical fiber and converting the incident light into a parallel light;

an optical device, for receiving the parallel light and performing predetermined optical processing on the parallel light;

a third optical fiber, optically coupled with the first lens, and having an axis in parallel with the optical axis of the first optical fiber and separated as much as a predetermined distance;

a second lens, for receiving a transmitted parallel light from the optical device and converging the transmitted parallel light to produce an outgoing light; and

a second optical fiber, optically coupled with the second lens, for receiving the outgoing light;

wherein the first lens has a focal point with a focal distance f, converges the parallel light reflected by the optical device, produce a reflected outgoing light, and provides the reflected outgoing light to the third optical fiber, the method comprising the steps of;

arranging the first lens and the second lens so that an optical axis of the first lens and an optical axis of the second lens are substantially coincident with each other;

arranging the optical device at a predetermined position between the first lens and the second lens so that a displacement amount from a focal point of the first lens is within ±

25% of a focal length of the first lens;

coupling the first and the third optical fibers with the first lens so that each of a vertical oblique angle θ

x and a horizontal oblique angle θ

y with respect to the optical axis of the first lens is within 0.2 degrees; and

coupling the second optical fiber with the second lens so that each of a vertical oblique angle θ

x and a horizontal oblique angle θ

y with respect to the optical axis of the second lens is within 0.2 degrees.

25. The method for assembling the optical module according to claim 24, wherein the second lens has a focal point with a focal distance f, the step for arranging the lens includes arranging the first lens and the second lens so that a distance between the first lens and the second lens (WD) is within a range of 2f±

2f/4.

26. The method for assembling the optical module according to claim 25, wherein the step of arranging the lens includes arranging the first lens and the second lens so that a displacement between an optical axis of the first lens and an optical axis of the second lens is within a range of 2.5% of the focal length f.

27. The method for assembling the optical module according to claim 24, wherein the first lens includes a first oblique plane which inclines with respect to the optical axis of the first lens and is optically coupled with the first optical fiber, and the second lens includes a second oblique plane which inclines with respect to the optical axis of the second lens and is optically coupled with the second optical fiber, and

a relative rotational displacement angle θ

z of the first and the second oblique planes is defined about the optical axes of the first and the second lenses as an rotation axis, and

the step for arranging the lens includes arranging the first lens and the second lens so that the relative rotational displacement angle θ

z of the first and the second oblique planes is within 20 degrees.

28. The method for assembling the optical module according to claim 24, wherein the step for arranging the lens includes to arrange the first lens and the second lens so that a vertical inclination of the first lens with respect to the optical axis of the first lens is within 1.5 degrees, and a vertical inclination of the second lens with respect to the optical axis of the second lens is within 1.5 degrees.

29. The method for assembling the optical module according to claim 28, wherein the first lens opposes to the second lens and has an emitting end face to emit the parallel light,

the second lens opposes to the first lens and has an incident end face to introduce the parallel light,

the step for arranging the lens, further comprising the steps of:

arranging the first lens so that each of the vertical oblique angle θ

x and the horizontal oblique angle θ

y of the emitting end face of the first lens with respect to the optical axis of the first lens is within 10 degrees; and

arranging each of the vertical oblique angle θ

x and the horizontal oblique angle θ

y of the incident end face of the second lens with respect to the optical axis of the second lens is set within 10 degrees.

30. The method for assembling the optical module according to claim 29, wherein the first lens includes a first coupling end face with which the first optical fiber is optically coupled, and θ

x and the horizontal oblique angle θ

y of the coupling end face of the first lens with respect to the optical axis of the first lens is within 2.5 degrees; and

arranging the second lens so that each of the vertical oblique angle θ

x and the horizontal oblique angle θ

y of the coupling end face of the second lens with respect to the optical axis of the second lens is within 2.5 degrees.