Miniature variable optical attenuator

• US 6,130,984 A
• Filed: 03/04/1998
• Issued: 10/10/2000
• Est. Priority Date: 05/19/1997
• Status: Expired due to Fees

• Current Assignee: JDS Uniphase Corporation (Lumentum Holdings Inc.)
• Original Assignee: E-Tek Dynamics Inc. (Lumentum Holdings Inc.)
• Inventors: Xu, Jingyu, Pan, Jing-Jong, Shen, Ronggui
• Primary Examiner(s): Lee, John D.
• Assistant Examiner(s): Stahl, Michael J.
• Application Number:
  US09/034,631
• Time in Patent Office: 951 Days
• Field of Search: 385/140, 385/47, 359/888, 359/889
• US Class Current: 385/140
• CPC Class Codes: G02B 3/0087 with index gradient
• CPC Class Codes: G02B 6/241 Light guide terminations
• CPC Class Codes: G02B 6/262 Optical details of coupling light into, or out of, or between fibre ends, e.g. special fibre end shapes or associated optical elements
• CPC Class Codes: G02B 6/266 the optical element being an attenuator
• 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

A variable optical attenuator controllably filters an optical signal after the signal has been expanded and collimated. The optical signals are optionally expanded and refocused by a single GRIN lens, the signal passing through a variable filter between the GRIN lens and a reflector, and again between the reflector and the GRIN lens. Both the input and output fibers can be held within a single sleeve in alignment with the GRIN lens. Alternatively, separate input and output GRIN lenses may be used. The amount of attenuation can be indicated by a potentiometer.

Claims

1. A variable attenuator comprising:

an electrical component having a body that defines a linear path and an element which is movable along the path to vary an electrical characteristic of the component;

an input optical fiber having an end with a dejacketed end portion adjacent the end, the dejacketed end portion having a core surrounded by a cladding;

an output optical fiber affixed in an optical path of an optical signal from the input fiber, the output optical fiber having an end with a dejacketed end portion adjacent the end, the dejacketed end portion having a core surrounded by a cladding;

a reflector affixed in the optical path between the input fiber and the output fiber;

an optical filter having a filter density which varies between a lower density region and a higher density region along a linear filter axis parallel to the path, an effective region of the filter disposed in the optical path between the input fiber and the output fiber, the filter affixed to the element so that the effective filter region moves between the low density region and the high density region in response to the element of the component moving along the path, whereby the electrical characteristic of the component indicates effective filter density, the filter moveably disposed in the optical path between the input fiber and the reflector, the filter also moveably disposed in the optical path between the reflector and the output fiber;

a collimating GRIN lens disposed in the optical path between the input fiber and the output fiber for expanding and collimating the optical signal transmitted therebetween; and

a ferrule, the end portion of the input fiber and the end portion of the output fiber disposed in a common lumen of the ferrule adjacent the collimating GRIN lens so that the cladding of the input fiber is in contact with the cladding of the output fiber adjacent the ends of the input and output fibers.

2. A variable attenuator as claimed in claim 1, wherein:

the component comprises a potentiometer and the element comprises a wiper; and

the optical filter is coupled to the wiper so that the effective filter density and a resistance of the potentiometer vary jointly as the effective filter region moves between the low density region and the high density region when the wiper of the potentiometer moves along the path, the electrical characteristic comprising the resistance.

3. A variable attenuator as claimed in claim 2, further comprising a circuit coupled to the potentiometer to sense and indicate the resistance, whereby attenuation of the effective filter region is indicated.

4. A variable attenuator as claimed in claim 2, wherein the filter is mounted on the wiper.

5. A variable attenuator as claimed in claim 4, further comprising a rotatable screw coupling the wiper to the body so that the wiper translates along an axis of the screw when the screw rotates relative to the body.

6. A variable attenuator as claimed in claim 5, further comprising an electrical motor coupled to the screw to controllably rotate the screw relative to the body.

7. A variable attenuator as claimed in claim 1, which further includes an electric motor operatively connected to the electric component selectively to drive the element to move along the path.

8. A variable attenuator as claimed in claim 7, further comprising a housing, the electrical component and the electric motor being contained within the housing.

9. A variable attenuator as claimed in claim 1, wherein the unjacketed end portions comprise single mode fiber portions having a diameter of about 125 μ

m, and wherein the lumen has a diameter of about 250 μ

m.

10. A variable attenuator comprising:

a housing;

a potentiometer disposed within the housing, the potentiometer having a body that defines a linear path, a wiper, and a rotatable screw coupling the wiper to the body to translate the wiper along the path when the screw rotates relative to the body;

an input optical fiber having an end with a dejacketed end portion adjacent the end, the dejacketed end portion having a core surrounded by a cladding;

an output optical fiber having an end with a dejacketed end portion adjacent an end, the dejacketed end portion having a core surrounded by a cladding;

a sleeve holding the end portions of the input optical fiber and the output optical fiber relative to the housing so that the cladding of the input fiber is in contact with the cladding of the output fiber adjacent the ends;

a GRIN lens disposed in an optical path of an optical signal from the input fiber;

a reflector disposed in the optical path from the GRIN lens, the reflector aligned to direct the signal back through the GRIN lens and into the output fiber;

an optical filter having an effective filter region disposed in the optical path between the GRIN lens and the reflector, the filter having a filter density which increases from a lower density region to a higher density region, the filter affixed to the wiper so that the effective region moves between the low density region and the high density region in response to the wiper moving relative to the body when the screw rotates; and

a circuit coupled to the potentiometer to sense an electrical signal which indicates a position of the wiper along the path, whereby effective attenuation of the attenuator is also indicated.

11. A variable attenuator as claimed in claim 10, wherein the GRIN lens and reflector are affixed to the housing, and further comprising an electrical motor coupled to the screw to controllably rotate the screw relative to the housing.

12. A variable attenuator as claimed in claim 11, wherein the electrical motor is mounted within the housing.

13. A variable attenuator as claimed in claim 12, which includes electrical motor connectors on the housing and which are electrically connected to the electrical motor.

14. A variable attenuator as claimed in claim 10, wherein the potentiometer is mounted within the housing.

15. A variable attenuator as claimed in claim 14, which includes potentiometer connectors on the housing and which are electrically connected to the potentiometer.

16. A variable attenuator as claimed in claim 10, wherein the sleeve defines a slant angled face which is in close proximity to a reciprocally slanted face of the GRIN lens.