Optical waveguides – With disengagable mechanical connector – Optical fiber to a nonfiber optical device connector
Reexamination Certificate
1998-05-07
2001-08-21
Henry, Jon (Department: 2872)
Optical waveguides
With disengagable mechanical connector
Optical fiber to a nonfiber optical device connector
Reexamination Certificate
active
06276843
ABSTRACT:
The present invention relates to connectors for coupling electromagnetic and in particular laser radiation into and out of optical fibres and components therefor. It relates in particular to connectors in which the alignment between the optical fibre and connector can be adjusted to optimise the transmission of radiation into and out of the optical fibre.
In many optical applications, electromagnetic radiation is transmitted along optical fibres and must therefore be coupled into the fibre at one end (for example from a laser source) and coupled out of the fibre at the other end into, for example, another fibre or some other optical component. In order to do this the radiation is typically focused on to the fibre end by one or more lenses, and lenses are similarly provided at the other end of the fibre to focus or collimate the exiting radiation.
One problem with such an arrangement is that both lateral misalignment between the optical axis of the fibre and the optical axis of the lens (or other optical component) and relative tilt between the central axes of the lens and fibre can lead to energy losses as the radiation is coupled into or out of the optical fibre.
In order to help reduce losses due to poor alignment between the fibre and lens (or other optical element), the end of the optical fibre and the lens are typically both mounted in a cylindrical tube in a predetermined fixed alignment with each other. This assembly is usually known as a lens barrel or a lens tube. The lens barrel holds the lens and fibre in a fixed, aligned relationship, thereby helping to avoid losses due to misalignment between the lens and fibre in use.
However, even with such an arrangement, losses can still occur due to misalignment between the fixed fibre and lens in the lens barrel and the laser source or other optical component to which the optical fibre is being optically coupled.
For example, any lateral displacement of the fibre and lens with respect to the incident radiation will cause the radiation impinging on the fibre end to be incident at an angle to the optical axis of the fibre. This could mean that some of the incident radiation falls outside the acceptance angle of the fibre, thereby leading to losses.
Any tilt of the central axis of the radiation source with respect to the central axis of the fibre and lens arrangement will cause the focused radiation to be displaced across the end face of the fibre. This may result in some radiation missing the fibre end face.
These situations can be common when coupling radiation from a laser or other sources into an optical fibre, and in both cases, the coupling efficiency will be degraded.
The change in coupling efficiency is proportional to exp−(&thgr;/&thgr;
div
)
2
and exp−(d/&rgr;)
2
where &thgr; is the angle between the radiation incident on the fibre face and the optical axis of the fibre, &thgr;
div
is half the acceptance angle of the fibre, d is the displacement of the radiation incident on the fibre face and &rgr; is the mode size of the fibre. Typical values for &rgr; and &thgr;
div
are 3 &mgr;m and 100 milliradians. The typical precision required for adjustment is therefore to within 50 &mgr;m and 10 microradians.
A similar situation can arise with the radiation emerging from an optical fibre where alignment with other optical components is required, or radiation needs to be coupled from one optical fibre to another (either with or without additional components in between).
In order to reduce these alignment losses, it is desirable to be able to adjust the alignment of the lens barrel and the laser source or other optical component to which the optical fibre is being coupled in use. In order to achieve this, the lens barrel is typically coupled to the laser source or optical component by means of a connector which allows the position of the lens barrel (and thus the fibre and lens) with respect to the laser source or optical component to be adjusted. Such a connector would typically provide adjustment of both tilt and lateral displacement, although the adjustable parameters may vary depending upon the application concerned.
A known prior art connector is shown in FIG.
1
. It comprises a cylindrical tube
1
which can receive a lens barrel
2
in use. The tube has two pairs of adjustments screws
3
a
,
3
b
and
4
a
,
4
b
, which extend through the tube and can engage the outer surface of the lens barrel once it has been inserted for adjusting the position of the lens barrel within the tube. An adjustable spring
5
is provided in an opposed relationship to the screws
3
a
,
3
b
,
4
a
,
4
b
to resiliently bias the lens barrel into engagement with the tips of the adjustment screws. The connector can be fixed to the optical component, laser source, etc., to which the optical fibre
6
is to be coupled by means of a flange
7
.
In use, the lens barrel is inserted into the tube
1
, and the spring
5
adjusted to resiliently bias it against the adjustment screws
3
a
,
3
b
,
4
a
,
4
b
. The screws
3
a
,
4
a
or
3
b
,
4
b
can then be moved together to move the lens barrel laterally (i.e. in a plane perpendicular to the axis of the lens barrel), or the screws
3
a
,
3
b
or
4
a
,
4
b
can be moved together to tilt the lens barrel in order to align the lens and optical fibre with the laser source, optical component, etc.
However, the Applicants have recognised a number of problems with this prior art connector.
One such problem is that because the adjustment screws engage the curved surface of the lens barrel, then adjustment of one screw to cause lateral displacement in one direction also causes lateral displacement in the direction of adjustment of the other adjustment screw as that screw moves around the curved surface of the lens barrel. This crosstalk between adjustment movements can make precise adjustment of the position of the lens barrel more difficult.
Another problem that the applicant's have recognised is that the lens barrel can be inserted in the connector at any orientation with respect to rotation about its longitudinal axis.
According to a first aspect of the present invention, there is provided an adjustable connector system for coupling an optical fibre assembly to an optical component, comprising:
a carrier means having a body having a throughbore adapted to receive the optical fibre assembly in use;
and a manipulator means having a body having a throughbore adapted to receive removably the carrier means and optical fibre assembly in use, the manipulator means further including one or more adjustment means which are engageable against the outer surface of the carrier means when it is inserted in the manipulator means throughbore and are adjustable by a user to then move the carrier means relative to the manipulator means in a direction perpendicular to the longitudinal axis of the manipulator means throughbore, the adjustment means being arranged such that they can be used to adjust the tilt of the longitudinal axis of the carrier means relative to the longitudinal axis of the manipulator means throughbore;
the system further being arranged such that when the optical fibre assembly is inserted in the carrier means movement of said adjustment means to effect movement of said carrier means relative to the manipulator means causes corresponding movement of the optical fibre assembly relative to the manipulator means; and
wherein the carrier means includes one or more lands on its outer surface arranged such that the carrier means can be inserted into the manipulator means in such a way that the adjustment means will in use engage only the lands, the lands further being arranged such that the carrier means can only be so inserted into the manipulator means in one or more discrete orientations with respect to rotation about the longitudinal axis of the manipulator means throughbore.
In this aspect of the present invention, the rotational orientation of the carrier means or carrier with respect to the manipulator means in use can be fixed and reproduced reliably by inserting the carrier
Alcock Ian Peter
Pointer David James
Henry Jon
Liniak Berenato Longacre & White LLP
Orzechowski Karen Lee
Point Source Limited
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