High precision optical collimator for optical waveguide

Details High precision optical collimator for optical waveguide High precision optical collimator for optical waveguide

2000-07-11

2002-01-22

Ullah, Akm E. (Department: 2874)

Optical waveguides

With disengagable mechanical connector

Optical fiber/optical fiber cable termination structure

C385S052000, C385S078000, C385S084000

Reexamination Certificate

active

06340248

ABSTRACT:

FIELD OF THE INVENTION
The invention relates generally to optical communication systems and, more specifically, to optical collimators used in optical communication systems.
BACKGROUND OF THE INVENTION
Optical communication systems use collimating lenses to transfer light from optical waveguides or fibers to other optical elements. Typically, light exiting an optical fiber will rapidly diverge. In order to efficiently transmit the optical signal, it is desirable to capture as much of the diverging light as possible. Collimating the exiting light beam is one method to accomplish this. Collimating the light beam involves positioning a collimating lens to receive the optical signal in such a way that substantially parallel light exits the collimating lens. Ideally the end of the fiber should be cut at right angles to its axis so that the light exiting the fiber will be parallel to its axis. However, one major difficulty with this technique is that portions of the optical signal will be reflected by the end surface of the cut fiber and propagated in a reverse direction through the optical fiber. This is an undesirable condition known as back reflection. One way to minimize back reflections is to cut the end of the optical fiber at an angle so that reflected light is not guided in the fiber. In this way, much of the reflected light will be lost and not returned through the optical fiber.
One way to minimize back reflection is shown in
FIG. 1
, where the end of an optical fiber
10
contained within ferrule
20
is polished at the standard Angular Physical Contact (APC) angle of 8°. As a result, a principle light beam coming out of the end of the fiber deviates from the fiber axis. The resultant angle of the light beam exiting the fiber can be shown, using Snell's law, to be approximately 3.62° (shown as angle
26
) for a typical communication fiber. To properly align fiber
10
to a collimating lens
12
, a ferrule
20
containing the fiber
10
is inserted into a collimator housing
22
and the angle
26
of the ferrule
20
to the axis
24
should be 3.62° to ensure that the light exiting the fiber along the axis
24
is coincident with the axis
13
of the collimating lens
12
.
Although the axis of the fiber
10
is aligned to the axis of the ferrule
20
, it is difficult to reliably and consistently align the ferrule
20
to the housing
22
at the correct angle and in the correct location. Any misalignment will result in degraded collimation. In the event that the end of the fiber
10
is misaligned, for example if it is located at point
25
instead of point
23
, or if its actual angle
26
does not accurately compensate for the angle of the light beam exiting the fiber
10
, the light exiting collimator lens
12
will deviate from the desired axis
24
. In order to construct a transverse spatial mode transformer, such as the one described in pending U.S. patent applications Ser. No. 09/249,830, 09/248,969 and 09/249,920 all filed on Feb. 12, 1999 whose contents are incorporated by reference and which are assigned to the assignee of this application, the collimation must be sufficiently accurate. Prior art methods generally are either cost prohibitive or not accurate enough to be used in precision applications.
SUMMARY OF THE INVENTION
The present invention relates to a multi-element assembly and a method for aligning a first component and a second component inside the assembly. The multi-element assembly includes an object having spherical surface, a first component, and a second component. The object includes a first bore and a second bore. The first and second bores have longitudinal axes which intersect at a predetermined angle. In one embodiment the object has a center and the longitudinal axes of the first and second bores intersect the center. In another embodiment the first component is an optical fiber. In another embodiment the second component is a lens. In a further embodiment, the lens is a collimating lens.
The method includes the steps of providing an object having a spherical surface and generating a first bore and a second bore in the object. The first and second bores have longitudinal axes which intersect at a predetermined angle. The method also includes the steps of positioning a first component in the first bore at a first position and positioning a second component in the second bore at a second position. In one embodiment the first and second components are separated by a predetermined distance.


REFERENCES:
patent: 4596406 (1986-06-01), Van Vleet et al.
patent: 5148322 (1992-09-01), Aoyama et al.
patent: 5347605 (1994-09-01), Isaksson
patent: 5898805 (1999-04-01), Kanazawa et al.
patent: 5963684 (1999-10-01), Ford et al.

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