GB2560494A

GB2560494A - Improvements in or relating to optical devices

Info

Publication number: GB2560494A
Application number: GB1702415.9A
Authority: GB
Inventors: Neil Kean Peter; Howard Legg Thomas; Webb Richard
Original assignee: Gooch & Housego Torquay Ltd
Current assignee: Gooch & Housego Torquay Ltd
Priority date: 2017-02-15
Filing date: 2017-02-15
Publication date: 2018-09-19
Anticipated expiration: 2037-02-15
Also published as: GB201702415D0; GB2560494B

Abstract

A collimated light attenuation apparatus 10 comprising: a light input device 12; a light output device 14; and a collimated light attenuation device 16 located between the input and output devices. The collimated light attenuation device is moveable between a minimum and maximum attenuation position. The collimated light attenuation member may include a threaded bore that engages with a screw member 24 arranged perpendicularly to the optical light path, the screw member being operated by an adjustment screw 26 to translate the attenuation member in a direction perpendicular to the optical light path. A biasing device 28 may bias the collimated light attenuation member towards the second maximum attenuation position. The apparatus may comprise a moveable collimated light reflection component 18 to reflect light from the input device to the output device. The collimated light input and output devices may be optical fibres.

Description

(54) Title of the Invention: Improvements in or relating to optical devices Abstract Title: Collimated light attenuation apparatus (57) A collimated light attenuation apparatus 10 comprising: a light input device 12; a light output device 14; and a collimated light attenuation device 16 located between the input and output devices. The collimated light attenuation device is moveable between a minimum and maximum attenuation position. The collimated light attenuation member may include a threaded bore that engages with a screw member 24 arranged perpendicularly to the optical light path, the screw member being operated by an adjustment screw 26 to translate the attenuation member in a direction perpendicular to the optical light path. A biasing device 28 may bias the collimated light attenuation member towards the second maximum attenuation position. The apparatus may comprise a moveable collimated light reflection component 18 to reflect light from the input device to the output device. The collimated light input and output devices may be optical fibres.

Fig. 1

1/6

co

CM

2/6

O

CN σ>

CD

CM co

CM

CO

M-

O

Fig. 3c

6/6

ο co .05

^r

co co .05

Improvements in or relating to optical devices

Field of the invention

This invention relates to a collimated light attenuation apparatus, an attenuation device for the same, a collimated variable optical delay line, a method of assembling a collimated light attenuation apparatus and an optical fibre collimator.

Background to the invention

It is desirable in certain optical equipment, such as optical delay lines, to provide the capability to attenuate the collimated light beam.

It is known to provide attenuation in such systems via a screw member which is screwed through the housing of the device and into, or out of, the path of the collimated light beam.

While such attenuation devices are capable of providing attenuation to the collimated light beam, they are limited in that it is difficult to ensure that the screw member intersects the light beam properly if the beam path is not very well defined, or positioned. Furthermore, it is often difficult, or not possible, to ensure that the screw member is long enough to fully intersect the beam. This means that the attenuation device may not be capable of providing 100% attenuation of the beam. Alternatively, if the screw member is too long, it may protrude from the housing of the device, which is undesirable.

In addition to this, other components, such as retroreflectors in optical delay lines, are very sensitive to the height and parallelism of collimated light beams entering and leaving the component. To fibre couple these components it is necessary to very accurately align the collimated light beams to the axis of the component. If the tolerance stack underneath the component and the input/output collimators is too large this can result in aligned collimators varying in height above the baseplate (or ceramic pad) to which they are attached. This is undesirable because it affects the performance and manufacture of the product, as variable thicknesses of adhesive behave differently both during cure at manufacture and under environmental changes in the finished product.

Ideally the gap between the collimator and the substrate to which it is attached should minimise the bond line thickness. The use of minimal adhesive minimises movement of the collimators upon cure and improves the performance of the fibre coupling to environmental changes.

The traditional approach to minimise this gap is to use a shim of material to pack out the variable gap or to have packages designed with different thickness baseplates. However, the implementation of these methods require additional manufacturing steps as the aligned collimators and package are disassembled, modified and reassembled. This is a time consuming and costly exercise.

The present inventors have appreciated the shortcomings in the existing optical equipment.

According to a first aspect of the present invention there is provided a collimated light attenuation apparatus comprising:

a collimated light input device; a collimated light output device; and a collimated light attenuation device located in the optical light path between the collimated light input device and the collimated light output device, wherein the collimated light attenuation device is configured to be 5 moveable between a first minimum attenuation position and a second maximum attenuation position, wherein the collimated light attenuation device is configured to be translatable between the first minimum attenuation position and the second maximum attenuation position.

The apparatus may be a free space beam collimated light attenuation apparatus. The free space may be the open space between the collimated light input device and the collimated light output device.

The term collimated light is intended to be considered as light whose rays are substantially parallel and spread minimally with propagation. That is, the collimated light may not be perfectly collimated with no divergence.

The collimated light input device may be capable of producing collimated light. The collimated light input device may be capable of producing collimated light from light in a fibre optic cable. The collimated light input device may be a fibre collimator. The collimated light may be delivered to a free space within the apparatus.

The collimated light output device may be capable of coupling collimated light into a fibre optic cable. The collimated light output device may be a fibre collimator.

The collimated light input device and the collimated light output device may be separate components. In this arrangement, the apparatus includes a collimated light input fibre collimator and a collimated light output fibre collimator. Each fibre collimator is associated with its own fibre optic cable. In this arrangement, collimated light from the collimated light input fibre collimator enters the free space between collimators and is received by the collimated light output fibre collimator. This arrangement may be termed a “transmissive” arrangement, or “two fibre” arrangement.

Alternatively, the collimated light input device and the collimated light output device may be a single component. In this arrangement, the apparatus includes a single collimated light input/output fibre collimator and a standard/auto collimator. The collimated light input/output fibre collimator includes a single fibre optic cable. In this arrangement, collimated light from the collimated light input/output fibre collimator enters the free space between collimators and is received by the standard/auto collimator and reflected to the collimated light input/output fibre collimator for transmission back into the fibre optic cable. The apparatus may also include all other necessary components to allow the beam to be reflected to the collimated light input/output fibre collimator, including mirrors, beam splitters and the like. This arrangement may be termed a “reflective” arrangement, or “single fibre” arrangement.

The optical light path may be considered the path that collimated light takes from the collimated light input device to the collimated light output device.

The term “translatable” used in the present application is considered as meaning moveable without rotation or angular displacement. That is, the collimated light attenuation device is moveable between the first minimum attenuation position and the second maximum attenuation position without rotation or angular displacement.

The collimated light attenuation device may be arranged to be translatable in a direction which is perpendicular to the optical light path.

The first minimum attenuation position may be a position in which the attenuation device does not attenuate the collimated light in the optical light path. The second maximum attenuation position may be a position in which the attenuation device attenuates the collimated light completely in the optical light path.

The collimated light attenuation device may be opaque. The collimated light attenuation device may be made from an opaque material.

The collimated light attenuation device may include a light attenuating member. The collimated light attenuating member may be a block or blade member. The block or blade member may be a generally rectangular cuboid member. The collimated light attenuation device may include one or more substantially planar surfaces, or outwardly facing surfaces.

The collimated light attenuation member may include a collimated light attenuating surface. The collimated light attenuating surface is the surface that the collimated light from the collimated light input device strikes during use of the apparatus. The collimated light attenuating surface may be a planar surface. The collimated light attenuating member may be configured such that the collimated light attenuating surface is substantially perpendicular to the optical light path. That is, the collimated light attenuating surface may be arranged such that, in use, the collimated light from the collimated light input device (i.e. the free space collimated light beam) is substantially perpendicular to the collimated light attenuating surface. Alternatively, the collimated light attenuating member may be configured such that the collimated light attenuating surface is offset, or non-perpendicular, to the optical light path. The collimated light attenuating surface may be offset from the perpendicular arrangement by between 4 and 10°. That is, the collimated light attenuating surface may be arranged such that, in use, it is slightly offset from perpendicular to a collimated light beam (i.e. the free space collimated light beam) from the collimated light input device.

io The collimated light attenuating surface may have an area that is at least the same size as the largest diameter of the collimated light from the collimated light input device. The collimated light attenuating surface may have an area that is greater than the largest diameter of the collimated light from the collimated light input device. In this arrangement, the collimated light attenuating surface can provide complete, or full (100%), attenuation of the collimated light beam.

The collimated light attenuating surface may have a collimated light beam engaging edge. The collimated light beam engaging edge may include a portion that is straight. The collimated light beam engaging edge may have a straight-edged portion.

The collimated light beam from the collimated light input device may be substantially circular with a horizontal and a vertical axis, and the collimated light beam engaging edge may be arranged to be parallel to the vertical axis of the collimated light beam. Alternatively, collimated light beam from the collimated light input device may be substantially circular with a horizontal and a vertical axis, and the collimated light beam engaging edge may be arranged to be offset to the vertical axis of the collimated light beam. The collimated light beam engaging edge may be offset from the vertical axis of the collimated light beam by between 15 and 45°.

The collimated light attenuation member may include a through bore. The through bore may be a threaded bore. The threaded bore may be configured to engage with a screw member. The threaded bore may include a female thread and the screw member may include a male thread. The screw member is configured to screw into and out of the threaded bore of the collimated light attenuation member.

io

The threaded bore may be arranged perpendicularly to the optical light path. The threaded bore may be arranged to be parallel to the direction of translation of the collimated light attenuation member. The screw member may be configured to be parallel to the threaded bore.

The collimated light attenuation device may include a housing member. The housing member may be configured to provide support to the collimated light attenuation member. The housing member may be configured to provide support to the screw member. The housing member may be configured to receive the screw member. The housing member may be configured to rotatably support the screw member. The screw member may be configured to rotate with respect to the housing member. The screw member may be configured to rotate with respect to the housing member such it does not translate with respect thereto. That is, the screw member may be configured to rotate within the housing member and not protrude inward or outward thereof.

The housing member may include a collimated light attenuation member receiving portion. The housing member may define the collimated light attenuation member receiving portion. The collimated light attenuation member receiving portion may be configured to receive the collimated light attenuation member and to guide the member between the first minimum attenuation position and the second maximum attenuation position. The collimated light attenuation member receiving portion may be arranged perpendicularly the optical light path and parallel to the threaded bore and screw member.

The collimated light attenuation member receiving portion may be a track member. The track member may be a channel member. The track member may define a channel portion.

The track member may include one or more wall portions. The wall portions being configured to support and guide the collimated light attenuation member as it translates between the first minimum attenuation position and the second maximum attenuation position.

The track member may be configured to allow translation of the collimated light attenuation member in a direction perpendicular to the optical light path and prevent translation of the collimated light attenuation member in a direction parallel to the optical light path. That is, the track member may be configured to only allow translation of the collimated light attenuation member therealong.

The track member may include one or more abutment, or stop, members.

The abutment, or stop, members may be configured to limit the travel of the collimated light attenuation member on the track member. The abutment, or stop, members may be configured to ensure that the collimated light attenuation member moves between the first minimum attenuation position and the second maximum attenuation position.

The collimated light attenuation device may include at least one adjustment screw. The at least one adjustment screw may be configured to operate the screw member. The adjustment screw may be tool, or hand, operated. The collimated light attenuation device may include two adjustment screws. Each adjustment screw may be located at opposite ends of the screw member. Each adjustment screw may be configured to operate the screw member.

The at least one, or each, adjustment screw may be configured to rotate with respect to the housing member.

The collimated light attenuation member, track member and screw member are configured such that, upon rotation of the screw member, the collimated light attenuation member translates along the track member with respect to the housing member. The collimated light attenuation member, track member and screw member are configured such that, upon rotation of the screw member, the collimated light attenuation member is prevented from rotating with the screw member and forced by the threaded bore and thread of the screw member to translate along the track member with respect to the housing member. Rotation of the screw member in a first direction causes movement of the collimated light attenuation member from the first minimum attenuation position towards the second maximum attenuation position, and rotation of the screw member in a second opposite direction causes movement of the collimated light attenuation member from the second maximum attenuation position to the first minimum attenuation position.

The collimated light attenuation device may further include a biasing device located between the collimated light attenuation member and the housing member. The biasing device may be configured to exert a bias force on the collimated light attenuation member to bias the collimated light attenuation member towards the second maximum attenuation position. Alternatively, the biasing device may be configured to exert a bias force on the collimated light attenuation member to bias the collimated light attenuation member towards the first minimum attenuation position.

The biasing device may be a spring member. The spring member may be located about the screw member. The screw member may be located within the spring member. The spring member may be a helical spring.

The collimated light input fibre collimator may be an optical fibre collimator. The optical fibre collimator may comprise a housing, a lens, an optical fibre ferrule and an optical fibre. The optical fibre may be mounted within the fibre ferrule. The optical fibre may be securely mounted to the fibre ferrule. The fibre ferrule may be mounted at least partially within the housing. The fibre ferrule may be securely mounted within the housing. The lens may be mounted within the housing. The lens may be securely mounted within the housing. The lens may be a light collimating lens. The optical fibre collimator may be configured such that light travelling in the optical fibre is collimated by the lens. Collimated light may then exit the optical fibre collimator.

The housing may be a longitudinal member. The housing may include a longitudinal axis. The longitudinal axis may be an axis of rotation. The longitudinal axis may be an axis of symmetry. The longitudinal axis may be a central axis. The longitudinal axis may be a mechanical axis. The longitudinal axis may be a central mechanical axis.

At least a portion of the optical fibre within the housing may be configured such that it coincides, or is coaxial, with the principle axis, or optical axis, of the lens. That is, at least a portion of the optical fibre lies lengthwise on the principle axis, or optical axis, of the lens. The optical axis of the light exiting the optical fibre may be aligned with the optical axis of the lens.

The longitudinal axis of the housing may coincide, or be coaxial, with the principle axis, or optical axis, of the lens. Alternatively, the longitudinal axis of the housing may be offset from the principle axis, or optical axis, of the lens. That is, the longitudinal axis of the housing may be spaced parallel from the principle axis, or optical axis, of the lens. In this arrangement, the longitudinal axis of the housing may be parallel to the principle axis, or optical axis, of the lens, but offset therefrom, i.e. separated by a lateral distance.

The longitudinal axis of the housing may be the centre of rotation of the housing. The longitudinal axis of the housing may be the rotational axis of the housing. The principle axis, or optical axis, of the lens may be the offcentre axis of the optical fibre collimator. In this arrangement, as the housing rotates, the principle axis, or optical axis, of the lens translates in a direction which is perpendicular to the longitudinal axis of the housing. Continued and repeated rotation of the housing causes the principle axis, or optical axis, of the lens to oscillate in a direction which is perpendicular to the longitudinal axis of the housing. The principle axis, or optical axis, of the lens may function as a cam as the housing is rotated.

The housing may be a cylindrical member. The housing may have a circular lateral cross section.

The housing may have a polygon-shaped lateral cross section. The housing may have an irregular polygon-shaped lateral cross section. The housing may have a rectangular-shaped lateral cross section. The housing may have an octagon-shaped lateral cross section. The housing may have a D-shaped lateral cross section.

The collimated light output fibre collimator may be an optical fibre collimator. The optical fibre collimator may comprise a housing, a lens, an optical fibre ferrule and an optical fibre. The optical fibre may be mounted within the fibre ferrule. The optical fibre may be securely mounted to the fibre ferrule. The fibre ferrule may be mounted at least partially within the housing. The fibre ferrule may be securely mounted within the housing. The lens may be mounted within the housing. The lens may be securely mounted within the housing. The lens may be a light collimating lens. The optical fibre collimator may be configured such that collimated light travelling into the lens is coupled by the lens into the optical fibre.

At least a portion of the optical fibre within the housing may be configured such that it coincides, or is coaxial, with the principle axis, or optical axis, of the lens. That is, at least a portion of the optical fibre lies lengthwise on the principle axis, or optical axis, of the lens.

The standard/auto collimator may comprise a housing and a lens. The lens may be mounted within the housing. The lens may be securely mounted within the housing. The lens may be a light collimating lens. The standard/auto collimator may be configured such that collimated light travelling into the lens is coupled by the lens into the optical fibre of the collimated light input fibre collimator.

The collimated light attenuation apparatus may include a base plate. The baseplate may provide support to the components of the apparatus.

The collimated light input device and the collimated light output device may be secured to the base plate. The collimated light input device and the collimated light output device may be secured to the base plate with a polyepoxide, epoxy resin, or the like.

The standard/auto collimator may be secured to the base plate. The standard/auto collimator may be secured to the base plate with a polyepoxide, epoxy resin, or the like.

The collimated light attenuation apparatus may further include one or more ceramic pads. The one or more ceramic pads may be attached to the base plate and the collimated light input device and the collimated light output device may be mounted thereon. The collimated light input device and the collimated light output device may be secured to the ceramic pads with a polyepoxide, epoxy resin, or the like.

The standard/auto collimator may be secured to the one or more ceramic pads. The standard/auto collimator may be secured to the one or more ceramic pads with a polyepoxide, epoxy resin, or the like.

The collimated light attenuation apparatus may further comprise a collimated light reflection component. The collimated light reflection component may be configured to reflect collimated light from the collimated light input device to the collimated light output device. The collimated light reflection component may be configured to reflect collimated light from the collimated light input device to the collimated light output device via the standard/auto collimator. The collimated light reflection component may be a retroreflector.

The collimated light reflection component may be moveable with respect to the collimated light input device and the collimated light output device. That is, the distance that the collimated light reflection component is located from the collimated light input device and the collimated light output device may be varied.

The collimated light attenuation apparatus may further comprise a chassis. The chassis may provide support to the collimated light reflection component.

The collimated light attenuation apparatus may further comprise a carriage. The carriage may be moveable with respect to the collimated light input device and the collimated light output device. That is, the distance that the carriage is located from the collimated light input device and the collimated light output device may be varied. The carriage may support the collimated light reflection component. The collimated light reflection component may be secured to the carriage.

The collimated light attenuation apparatus may further comprise a motor. The motor may be operable to move the carriage. The carriage may be motor driven. The motor may be a stepper motor. The carriage may be mounted to a screw member driven by the motor, such that rotation of the screw member by the motor causes translation of the carriage along the chassis.

Varying the distance between the collimated light reflection component and the collimated light input device and the collimated light output device varies the optical light path length.

The chassis may comprise travel limiting abutments. The travel limiting abutments may control the minimum and maximum distance of the collimated light reflection component from the collimated light input device and the collimated light output device. The travel limiting abutments may be optical switches. The travel limiting abutments may also include optical switches. The optical switches being configured to control the operation of the motor and thus control the minimum and maximum distance of the collimated light reflection component from the collimated light input device and the collimated light output device.

According to a second aspect of the present invention there is provided a collimated light attenuation device comprising:

a collimated light attenuating member;

a screw member; and a housing member, wherein the collimated light attenuating member includes a threaded bore, the threaded bore configured to receive and engage with the screw member, wherein the housing member is configured to provide support to the collimated light attenuating member and the screw member, wherein the housing member is arranged to permit movement of the collimated light attenuating member between a first position on the housing member and a second position on the housing member upon rotation of the screw member.

The collimated light attenuation device may be configured for use with a collimated light apparatus. The collimated light apparatus may be a collimated light variable optical delay line.

The collimated light apparatus may comprise a collimated light input device and a collimated light output device.

The collimated light attenuation device may be configured such that it may be locatable in the optical light path between the collimated light input device and the collimated light output device.

The collimated light attenuation device may be operable such that the collimated light attenuating member is moveable between a first minimum attenuation position and a second maximum attenuation position.

The collimated light attenuating member may be translatable between the first minimum attenuation position and the second maximum attenuation position.

The collimated light apparatus may be a free space beam collimated light attenuation apparatus. The free space may be the open space between the collimated light input device and the collimated light output device.

Alternatively, the collimated light input device and the collimated light output device may be a single component. In this arrangement, the apparatus includes a single collimated light input/output fibre collimator and a standard/auto collimator. The collimated light input/output fibre collimator includes a single fibre optic cable. In this arrangement, collimated light from the collimated light input/output fibre collimator enters the free space between collimators and is received by the standard/auto collimator and reflected to the collimated light input/output fibre collimator for transmission back into the fibre optic cable. This arrangement may be termed a “reflective” arrangement, or “single fibre” arrangement.

The term “translatable” used in the present application is considered as meaning moveable without rotation or angular displacement. That is, the collimated light attenuation member is moveable between the first position and the second position without rotation or angular displacement.

The collimated light attenuation member may be arranged to be translatable in a direction which is perpendicular to the optical light path.

The first minimum attenuation position may be a position in which the attenuation member does not attenuate the collimated light in the optical light path. The second maximum attenuation position may be a position in which the attenuation member attenuates the collimated light completely in the optical light path.

The collimated light attenuation member may be opaque. The collimated light attenuation member may be made from an opaque material.

The collimated light attenuating member may be a block or blade member. The block or blade member may be a generally rectangular cuboid member. The collimated light attenuation device may include one or more substantially planar surfaces, or outwardly facing surfaces.

The collimated light attenuation member may include a collimated light attenuating surface. The collimated light attenuating surface is the surface that the collimated light from the collimated light input device strikes during use of the device. The collimated light attenuating surface may be a planar surface. The collimated light attenuating member may be configured such that the collimated light attenuating surface is substantially perpendicular to the optical light path. That is, the collimated light attenuating surface may be arranged such that, in use, the collimated light from the collimated light input device (i.e. the free space collimated light beam) is substantially perpendicular to the collimated light attenuating surface. Alternatively, the collimated light attenuating member may be configured such that the collimated light attenuating surface is offset, or non-perpendicular, to the optical light path. The collimated light attenuating surface may be offset from the perpendicular arrangement by between 4 and 10°. That is, the collimated light attenuating surface may be arranged such that, in use, it is slightly offset from perpendicular to a collimated light beam (i.e. the free space collimated light beam) from the collimated light input device.

The collimated light attenuating surface may have an area that is at least the same size as the largest diameter of the collimated light from the collimated light input device. The collimated light attenuating surface may have an area that is greater than the largest diameter of the collimated light from the collimated light input device. In this arrangement, the collimated light attenuating surface can provide complete, or full (100%), attenuation of the collimated light beam.

The collimated light beam engaging edge may be arranged perpendicularly with respect to the optical light path. That is, the collimated light beam from the collimated light input device may be substantially circular with a horizontal and a vertical axis, and the collimated light beam engaging edge may be arranged to be parallel to the vertical axis of the collimated light beam. Alternatively, the collimated light beam engaging edge may be arranged to be offset with respect to the optical light path. That is, the collimated light beam from the collimated light input device may be substantially circular with a horizontal and a vertical axis, and the collimated light beam engaging edge may be arranged to be offset to the vertical axis of the collimated light beam. The collimated light beam engaging edge may be offset from the vertical axis of the collimated light beam by between 15 and 45°.

The threaded bore may include a female thread and the screw member may include a male thread. The screw member is configured to screw into and out of the threaded bore of the collimated light attenuation member.

The housing member may be configured to receive the screw member.

The housing member may be configured to rotatably support the screw member. The screw member may be configured to rotate with respect to the housing member. The screw member may be configured to rotate with respect to the housing member such it does not translate with respect thereto. That is, the screw member may be configured to rotate within the housing member and not protrude inward or outward thereof.

The housing member may include a collimated light attenuation member receiving portion. The housing member may define the collimated light attenuation member receiving portion. The collimated light attenuation member receiving portion may be configured to receive the collimated light attenuation member and to guide the member between the first position and the second position. The collimated light attenuation member receiving portion may be arranged perpendicularly the optical light path and parallel to the threaded bore and screw member.

The track member may include one or more wall portions. The wall portions being configured to support and guide the collimated light attenuation member as it translates between the first position and the second position.

The track member may include one or more abutment, or stop, members. The abutment, or stop, members may be configured to limit the travel of the collimated light attenuation member on the track member. The abutment, or stop, members may be configured to ensure that the collimated light attenuation member moves between the first position and the second position.

The collimated light attenuation member may include at least one adjustment screw. The at least one adjustment screw may be configured to operate the screw member. The adjustment screw may be tool, or hand, operated. The collimated light attenuation member may include two adjustment screws. Each adjustment screw may be located at opposite ends of the screw member. Each adjustment screw may be configured to operate the screw member.

The collimated light attenuation member, track member and screw member are configured such that, upon rotation of the screw member, the collimated light attenuation member translates along the track member with respect to the housing member. The collimated light attenuation member, track member and screw member are configured such that, upon rotation of the screw member, the collimated light attenuation member is prevented from rotating with the screw member and forced by the threaded bore and thread of the screw member to translate along the track member with respect to the housing member. Rotation of the screw member in a first direction causes movement of the collimated light attenuation member from the first position towards the second position, and rotation of the screw member in a second opposite direction causes movement of the collimated light attenuation member from the second position to the first position.

The collimated light attenuation device may further include a biasing device located between the collimated light attenuation member and the housing member. The biasing device may be configured to exert a bias force on the collimated light attenuation member to bias the collimated light attenuation member towards the second position. Alternatively, the biasing device may be configured to exert a bias force on the collimated light attenuation member to bias the collimated light attenuation member towards the first position.

The biasing device may be a spring member. The spring member may be a helical spring. The spring member may be located about the screw member. The screw member may be located within the spring member.

The collimated light input fibre collimator may be an optical fibre collimator.

The optical fibre collimator may comprise a housing, a lens, an optical fibre ferrule and an optical fibre. The optical fibre may be mounted within the fibre ferrule. The optical fibre may be securely mounted to the fibre ferrule. The fibre ferrule may be mounted at least partially within the housing. The lens may be mounted within the housing. The lens may be securely mounted within the housing. The lens may be a light collimating lens. The optical fibre collimator may be configured such that light travelling in the optical fibre is collimated by the lens. Collimated light may then exit the optical fibre collimator.

The collimated light output fibre collimator may be an optical fibre collimator. The optical fibre collimator may comprise a housing, a lens, an optical fibre ferrule and an optical fibre. The optical fibre may be mounted within the fibre ferrule. The optical fibre may be securely mounted to the fibre ferrule. The fibre ferrule may be mounted at least partially within the housing. The lens may be mounted within the housing. The lens may be securely mounted within the housing. The lens may be a light collimating lens. The optical fibre collimator may be configured such that collimated light travelling into the lens is coupled by the lens into the optical fibre.

The longitudinal axis of the housing may coincide, or be coaxial, with the principle axis, or optical axis, of the lens. Alternatively, the longitudinal axis of the housing may be offset from the principle axis, or optical axis, of the lens. That is, the longitudinal axis of the housing may be spaced parallel from the principle axis, or optical axis, of the lens. In this arrangement, the longitudinal axis of the housing may be parallel to the principle axis, or optical axis, of the lens, but offset therefrom, i.e.

separated by a lateral distance.

The longitudinal axis of the housing may be the centre of rotation of the housing. The longitudinal axis of the housing may be the rotational axis of the housing. The principle axis, or optical axis, of the lens may be the off10 centre axis of the optical fibre collimator. In this arrangement, as the housing rotates, the principle axis, or optical axis, of the lens translates in a direction which is perpendicular to the longitudinal axis of the housing. Continued and repeated rotation of the housing causes the principle axis, or optical axis, of the lens to oscillate in a direction which is perpendicular to the longitudinal axis of the housing. The principle axis, or optical axis, of the lens may function as a cam as the housing is rotated.

The longitudinal axis of the housing may be the centre of rotation of the housing. The longitudinal axis of the housing may be the rotational axis of the housing. The principle axis, or optical axis, of the lens may be the offcentre axis of the optical fibre collimator. In this arrangement, as the housing rotates, the principle axis, or optical axis, of the lens translates in a direction which is perpendicular to the longitudinal axis of the housing.

Continued and repeated rotation of the housing causes the principle axis, or optical axis, of the lens to oscillate in a direction which is perpendicular to the longitudinal axis of the housing. The principle axis, or optical axis, of the lens may function as a cam as the housing is rotated.

The collimated light input device and the collimated light output device may be secured to a base plate. The collimated light input device and the collimated light output device may be secured to the base plate with a polyepoxide, epoxy resin, or the like.

The collimated light input device and the collimated light output device may be mounted upon one or more ceramic pads. The ceramic pads may be mounted to the base plate. The collimated light input device and the collimated light output device may be secured to the ceramic pads with a polyepoxide, epoxy resin, or the like.

The collimated light attenuation device may further comprise a collimated light reflection component. The collimated light reflection component may be configured to reflect collimated light from the collimated light input device to the collimated light output device. The collimated light reflection component may be configured to reflect collimated light from the collimated light input device to the collimated light output device via the standard/auto collimator. The collimated light reflection component may be a retroreflector.

The collimated light reflection component may be moveable with respect to the collimated light input device and the collimated light output device.

That is, the distance that the collimated light reflection component is located from the collimated light input device and the collimated light output device may be varied.

The collimated light attenuation device may further comprise a chassis.

The chassis may provide support to the collimated light reflection component.

The collimated light attenuation device may further comprise a carriage. The carriage may be moveable with respect to the collimated light input device and the collimated light output device. That is, the distance that the carriage is located from the collimated light input device and the collimated light output device may be varied. The carriage may support the collimated light reflection component. The collimated light reflection component may be secured to the carriage.

The collimated light attenuation device may further comprise a motor. The motor may be operable to move the carriage. The carriage may be motor driven. The motor may be a stepper motor. The carriage may be mounted to a screw member driven by the motor, such that rotation of the screw member by the motor causes translation of the carriage along the chassis.

Embodiments of second aspect of the present invention may include one or more features of the first aspect of the present invention or its embodiments.

According to a third aspect of the present invention there is provided a collimated light variable optical delay line comprising:

a collimated light input device;

a collimated light output device;

a moveable collimated light reflection component, the collimated light reflection component being configured to reflect collimated light from the collimated light input device to the collimated light output device; and a collimated light attenuation apparatus located in the optical light path between the collimated light input device and the collimated light output device, wherein the collimated light attenuation device is configured to be 5 moveable between a first minimum attenuation position and a second maximum attenuation position, wherein the collimated light attenuation device is configured to be translatable between the first minimum attenuation position and the second maximum attenuation position.

Embodiments of third aspect of the present invention may include one or more features of the first or second aspects of the present invention or their embodiments.

According to a fourth aspect of the present invention there is provided a method of assembling a collimated light attenuation apparatus comprising the steps of:

providing:

a base portion;

a collimated light input device and a collimated light output device, wherein at least one of the collimated light input device and collimated light output device is an optical fibre collimator comprising a housing, a lens, an optical fibre ferrule and an optical fibre, and wherein the lens, and optical fibre ferrule are secured to the housing, and wherein the housing has a longitudinal rotational axis and the lens has a principle axis, and wherein the longitudinal rotational axis of the housing and the principle axis of the lens are offset from one another; and a collimated light attenuation device, wherein the collimated light attenuation device is configured to be translatable between a first minimum attenuation position and a second maximum attenuation position;

positioning the collimated light input device and a collimated light output device on the base portion;

rotating at least one of the collimated light input device and collimated light output device about its longitudinal rotational axis to a desired position;

fixing the collimated light input device and collimated light output device in position on the base portion; and locating the collimated light attenuation device in the optical path between the collimated light input device and the collimated light output device.

Embodiments of the fourth aspect of the present invention may include one or more features of the first, second or third aspects of the present invention or their embodiments.

According to a fifth aspect of the present invention there is provided an optical fibre collimator comprising:

a housing:

a lens;

an optical fibre ferrule; and an optical fibre, wherein the optical fibre is secured to the optical fibre ferrule and the lens and the optical fibre ferrule are secured to the housing, and wherein the housing has a longitudinal rotational axis and the lens has a principle axis, and wherein the longitudinal rotational axis of the housing and the principle axis of the lens are offset from one another.

Embodiments of the fifth aspect of the present invention may include one or more features of the first, second, third or fourth aspects of the present invention or their embodiments.

According to a sixth aspect of the present invention there is provided a collimated light variable optical delay line comprising:

a collimated light input device and a collimated light output device, wherein at least one of the collimated light input device and collimated light output device is an optical fibre collimator 15 comprising a housing, a lens, an optical fibre ferrule and an optical fibre, and wherein the lens, and optical fibre ferrule are secured to the housing, and wherein the housing has a longitudinal rotational axis and 20 the lens has a principle axis, and wherein the longitudinal rotational axis of the housing and the principle axis of the lens are offset from one another; and a moveable collimated light reflection component, the collimated light reflection component being configured to reflect collimated light from the collimated light input device to the collimated light output device.

Embodiments of the sixth aspect of the present invention may include one or more features of the first, second, third, fourth or fifth aspects of the present invention or their embodiments.

Brief description of the drawings

Embodiments of the invention will now be described, by way of example only, with reference to the following drawings, in which:

Fig. 1 is a perspective view of a collimated light attenuation apparatus according to the invention;

Figs. 2a to 2c are views of the collimated light attenuation apparatus according of Fig. 1 with the collimated light attenuation device in io a first minimum attenuation position;

Figs. 3a to 3c are views of the collimated light attenuation apparatus according of Fig. 1 with the collimated light attenuation device in a second maximum attenuation position;

Figs. 4a to 4c are views of the collimated light attenuation apparatus according of Fig. 1 with the collimated light attenuation device removed;

Fig. 5 is an alternate embodiment of the collimated light attenuation apparatus of Fig. 1; and

Figs. 6a to 6c are lateral cross section views of three alternate embodiments a collimated light input/output device according to the invention.

Description of embodiments of the invention

Referring to Figs. 1 through 4c, a collimated light attenuation apparatus 10 is illustrated. In the embodiment illustrated here the apparatus 10 is an optical delay line (an example of a collimated light variable optical delay line). However, it should be appreciated that the apparatus 10 may be any other apparatus where attenuation of a collimated light is required or desired.

The apparatus 10 includes a collimated light input device 12, a collimated light output device 14, a collimated light attenuation device 16, a moveable collimated light reflection component 18 and a motor 20.

The apparatus 10 is a free space beam collimated light attenuation apparatus, the free space being the open space between the collimated light input device 12 and the collimated light output device 14.

io The collimated light input device 12 is a fibre collimator and is capable of producing collimated light from the light in the fibre optic cable 12a. The collimated light input device 12 thus launches collimated light into the free space. The collimated light output device 14 is also a fibre collimator and is capable of coupling collimated light into the fibre optic cable 14a.

In the embodiment illustrated and descried here the collimated light input device 12 and the collimated light output device 14 are separate components. In this arrangement, the apparatus 10 includes a collimated light input fibre collimator 12 and a collimated light output fibre collimator

14. Each fibre collimator 12, 14 is associated with its own fibre optic cable

12a, 14a. In this arrangement, collimated light from the collimated light input fibre collimator 12 enters the free space between collimators and is received by the collimated light output fibre collimator 14, via the collimated light reflection component 18, described further below. This arrangement may be termed a “transmissive” arrangement, or “two fibre” arrangement.

However, it should be appreciated that the collimated light input device 12 and the collimated light output device 14 may be a single component. In this arrangement, the apparatus 10 includes a single collimated light input/output fibre collimator 13 and a standard/auto collimator 15. The collimated light input/output fibre collimator 13 includes a single fibre optic cable 13a. In this arrangement, collimated light from the collimated light input/output fibre collimator 13 enters the free space between collimators

13, 15 and is received by the standard/auto collimator 15 and reflected to the collimated light input/output fibre collimator 13 for transmission back into the fibre optic cable 13a. This arrangement may be termed a “reflective” arrangement, or “single fibre” arrangement. This alternate arrangement is illustrated in Fig. 5. All other components are identical to io the apparatus 10 described and illustrated herein.

The optical light path 22 is considered as the path that collimated light takes from the collimated light input device 12 to the collimated light output device 14, via the collimated light reflection component 18. The optical light path 22 is illustrated in Fig. 2c only.

The collimated light attenuation device 16 is located in the optical light path 22 between the collimated light input device 12 and the collimated light output device 14. As described further below, the collimated light attenuation device 16 may be configured to attenuate between 0% and 100% of the collimated light from the collimated light input device 12. The amount of attenuation provided by the device 16 is dependent upon its position relative to the free space beam provided by the collimated light input device 12.

With reference to Figs. 2a and 3a, the collimated light attenuation device, or member, 16 is configured to be moveable between a first minimum attenuation position (open position, Fig. 2a) and a second maximum attenuation position (closed position, Fig. 3a). As described further below, the collimated light attenuation device 16 translates between the first minimum attenuation position and the second maximum attenuation position. That is, the collimated light attenuation device 16 moves between the two positions without rotation or angular displacement relative to the apparatus 10. As will be appreciated from the accompanying figures, the collimated light attenuation device 16 is arranged to be translatable in a direction which is perpendicular to the optical light path

22.

In the embodiment illustrated and described here the collimated light io attenuation member 16 is an opaque rectangular block. However, it should be appreciated that the collimated light attenuation device 16 may have other suitable shapes.

The collimated light attenuation member 16 includes a collimated light attenuating surface 16a (Figs. 1,2c and 3c). The collimated light attenuating surface 16a is the surface that the collimated light from the collimated light input device 12 strikes during use of the apparatus 10.

The surface 16a is a planar surface and in the embodiment illustrated and described here is arranged to be perpendicular to the optical light path 22. That is, the surface 16a is arranged such that, in use, the collimated light from the collimated light input device 12 (i.e. the free space collimated light beam) is substantially perpendicular to the surface 16a. However, it should be appreciated that, in order to mitigate reflected light going back into the collimated light input device 12, the surface 16a may be offset, or non-perpendicular, to the optical light path 22. The collimated light attenuating surface 16a may be offset from the perpendicular arrangement by between 4 and 10°. That is, the collimated light attenuating surface 16a may be arranged such that, in use, it is slightly offset from perpendicular to a collimated light beam (i.e. the free space collimated light beam) from the collimated light input device 12.

The collimated light attenuating surface 16a has an area that is at least the same size as, or greater than, the largest diameter of the collimated light from the collimated light input device 12. In this arrangement, the collimated light attenuating surface 16a can provide complete, or full (100%), attenuation of the collimated light beam.

io As best illustrated in Fig. 1, the collimated light attenuating surface 16a has collimated light beam engaging edge 16b. The engaging edge 16b is straight, or has a straight portion.

The collimated light beam 12b from the collimated light input device 12 may be substantially circular with a horizontal axis 12c and a vertical axis 12d (Fig. 1), and the collimated light beam engaging edge 16b may be arranged to be parallel to the vertical axis 12d of the collimated light beam 12b.

However, in the embodiment illustrated and described here the collimated light beam engaging edge 16b is arranged to be offset with respect to the vertical axis 12d of the collimated light beam 12b. The collimated light beam engaging edge 16b may be offset from the vertical axis 12d of the collimated light beam 12b by between 15 and 45°. Providing a collimated light beam engaging edge 16b this is offset from the vertical axis 12d of the collimated light beam 12b increases the rate at which the collimated light beam 12b is attenuated as the collimated light attenuation member 16 moves across the apparatus 10.

As best illustrated in Fig. 1, the collimated light attenuation member 16 includes a threaded through bore 16c. The threaded bore 16c is configured to engage with a screw member 24. The threaded bore 16c may include a female thread and the screw member 24 may include a male thread. The screw member 24 is configured to screw into and out of the threaded bore 16c of the collimated light attenuation member 16. As illustrated, the threaded bore is arranged perpendicularly to the optical light path 22 and parallel to the direction of translation of the collimated light attenuation member 16. The screw member 24 is parallel to the io threaded bore 16c.

The collimated light attenuation device 16 may include a housing member 16d. The housing member 16d is configured to provide support to the collimated light attenuation member 16 and the screw member 24. The housing member 16d is configured to receive the screw member and rotatably support the screw member 24 therein. The screw member 24 therefore is configured to rotate with respect to the housing member 16d. Furthermore, the screw member 24 is configured to rotate with respect to the housing member 16d such it does not translate with respect thereto.

That is, the screw member 24 is configured to rotate within the housing member 16d and not protrude inward or outward thereof.

The housing member 16d includes a collimated light attenuation member receiving portion 16e (Figs. 4a to 4c). The collimated light attenuation member receiving portion 16e is configured to receive the collimated light attenuation member 16 and to guide the member 16 between the first minimum attenuation position and the second maximum attenuation position. The collimated light attenuation member receiving portion 16e is arranged perpendicularly the optical light path 22 and parallel to the threaded bore 16c and screw member 24. The collimated light attenuation member receiving portion 16e is a track member, or channel member, or channel portion.

The collimated light attenuation member receiving portion 16e includes wall portions 16f, the wall portions 16f being configured to support and guide the collimated light attenuation member 16 as it translates between the first minimum attenuation position and the second maximum attenuation position. The wall portions 16f are configured to allow translation of the collimated light attenuation member 16 in a direction io perpendicular to the optical light path 22 and prevent translation of the collimated light attenuation member 16 in a direction parallel to the optical light path 22. That is, the collimated light attenuation member receiving portion 16e is configured to only allow translation of the collimated light attenuation member 16 along its length.

The collimated light attenuation member receiving portion 16e includes abutments, or stop, members 16g. The abutment, or stop, members 16g are configured to limit the travel of the collimated light attenuation member

16. The abutment, or stop, members 16g are configured to ensure that the collimated light attenuation member 16 does not move below the first minimum attenuation position, as illustrated in Figs. 2a to 2c. The collimated light attenuation member 16 is prevented from moving past the second maximum attenuation position by abutting the housing member 16d, as illustrated in Figs. 3a to 3c.

The collimated light attenuation device 16 includes may include an adjustment screw 26. The adjustment screw 26 is configured to operate the screw member 24. The adjustment screw 26 may be tool, or hand, operated. The adjustment screw 26 is configured to rotate with respect to the housing member 16d.

With reference to Figs. 2a to 3c, the collimated light attenuation member 16, collimated light attenuation member receiving portion 16e, and screw member 24 are configured such that, upon rotation of the screw member

24 by the adjustment screw 26, the collimated light attenuation member 16 translates along the attenuation member receiving portion 16e with respect to the housing member 16d. The collimated light attenuation member 16, attenuation member receiving portion 16e and screw member 24 are configured such that, upon rotation of the screw member 24 by the io adjustment screw 26, the collimated light attenuation member 16 is prevented from rotating with the screw member 24 and forced by the threaded bore 16c and thread of the screw member 24 to translate along the attenuation member receiving portion 16e with respect to the housing member 16d. Rotation of the screw member 24 in a first direction causes movement of the collimated light attenuation member 16 from the first minimum attenuation position towards the second maximum attenuation position, and rotation of the screw member 24 in a second opposite direction causes movement of the collimated light attenuation member 16 from the second maximum attenuation position to the first minimum attenuation position.

The collimated light attenuation device 16 further includes a biasing device 28 located between the collimated light attenuation member 16 and the housing member 16d. The biasing device 28 may be configured to exert a bias force on the collimated light attenuation member 16 to bias the collimated light attenuation member 16 towards the second maximum attenuation position. In an alternate arrangement, the biasing device 28 may be configured to exert a bias force on the collimated light attenuation member 16 to bias the collimated light attenuation member 16 towards the first minimum attenuation position. In the embodiment illustrated and described here the biasing device 28 is a spring member which is located around the screw member 24. The spring member 28 minimises the risk of backlash of the collimated light attenuation member 16.

As described above, the collimated light input fibre collimator 12 is an optical fibre collimator. With reference to Figs. 1a to 4c and, in particular, Figs. 6a to 6c, the optical fibre collimator 12 may comprise a housing 12e, a lens 12f, an optical fibre ferrule 12g and the optical fibre 12a. The optical fibre 12a is mounted within the fibre ferrule 12g and secured io thereto. The fibre ferrule 12g is mounted at least partially within the housing 12e. The lens 12f is also securely mounted within the housing 12e. The lens 12f is a light collimating lens. As described above, the optical fibre collimator 12 is configured such that light travelling in the optical fibre 12a is collimated by the lens 12f. Collimated light may then exit the optical fibre collimator 12.

The housing 12e is a longitudinal member with a longitudinal axis 12h.

The longitudinal axis 12h is an axis of rotation. The longitudinal axis 12h may also be an axis of symmetry, a central axis, or a mechanical axis.

At least a portion of the optical fibre 12a within the housing 12e is configured such that it coincides, or is coaxial, with the principle axis 12i, or optical axis, of the lens 12f. That is, at least a portion of the optical fibre 12a lies lengthwise on the principle axis 12i, or optical axis, of the lens 12f.

In this arrangement the optical axis of the light exiting the optical fibre 12a is aligned with the optical axis of the lens 12f.

The longitudinal axis 12h of the housing 12e may coincide, or be coaxial, with the principle axis 12i, or optical axis, of the lens 12f. However, in the embodiment illustrated and described here the longitudinal axis 12h of the housing 12e is offset from the principle axis 12i, or optical axis, of the lens 12f. That is, the longitudinal axis 12h of the housing 12e is spaced parallel from the principle axis 12i, or optical axis, of the lens 12f. In this arrangement, the longitudinal axis 12h of the housing 12e is parallel to the principle axis 12i, or optical axis, of the lens 12f, but offset therefrom, i.e. separated by a lateral distance D, as illustrated in Fig. 6a.

As stated above, the longitudinal axis 12h of the housing 12e is the centre of rotation of the housing 12e, or the rotational axis of the housing 12e.

io The principle axis 12i, or optical axis, of the lens 12f is the off-centre axis of the optical fibre collimator 12. In this arrangement, as the housing 12e rotates, the principle axis 12i, or optical axis, of the lens 12f translates in a direction which is perpendicular to the longitudinal axis 12h of the housing 12e. Continued and repeated rotation of the housing 12e causes the principle axis 12i, or optical axis, of the lens 12f to oscillate in a direction which is perpendicular to the longitudinal axis 12h of the housing 12e.

The principle axis 12i, or optical axis, of the lens 12f may function as a cam as the housing 12e is rotated.

As illustrated in Figs. 1 to 4c and 6c, the housing 12e is a cylindrical member with a circular lateral cross section. However, it should be appreciated that the housing 12e may have other shapes with other lateral cross sections. By way of example only, the housing may have a polygonshaped lateral cross section, an irregular polygon-shaped lateral cross section (Fig. 6c), a rectangular-shaped lateral cross section, a D-shaped lateral cross section, or a octagon-shaped lateral cross section (Fig. 6b). Where the housing has a non-circular lateral cross section and there are one or more flat edges/flat surfaces on the housing, this may provide additional bond strength between the flat surface of the housing and a flat surface of the base plate or ceramic plate and the cured collimator assembly.

The collimated light output fibre collimator 14 is also an optical fibre collimator. The construction, arrangement and operation of the optical fibre collimator 14 may be identical to the optical fibre collimator 12. The optical fibre collimator 14 may also have the same alternate configurations as the optical fibre collimator 12.

io With reference to Figs. 1a to 4c and, in particular, Figs. 6a to 6c, the optical fibre collimator 14 may comprise a housing 14e, a lens 14f, an optical fibre ferrule 14g and the optical fibre 14a. The optical fibre 14a is mounted within the fibre ferrule 14g and secured thereto. The fibre ferrule 14g is mounted at least partially within the housing 14e. The lens 14f is also securely mounted within the housing 14e. The lens 14f is a light collimating lens. As described above, the optical fibre collimator 14 is configured such that collimated light travelling into the lens 14f is coupled by the lens 14f into the optical fibre 14a.

The housing 14e is a longitudinal member with a longitudinal axis 14h.

The longitudinal axis 14h is an axis of rotation. The longitudinal axis 14h may also be an axis of symmetry, a central axis, or a mechanical axis.

At least a portion of the optical fibre 14a within the housing 14e is configured such that it coincides, or is coaxial, with the principle axis 14i, or optical axis, of the lens 14f. That is, at least a portion of the optical fibre 14a lies lengthwise on the principle axis 14i, or optical axis, of the lens 14f.

The longitudinal axis 14h of the housing 14e may coincide, or be coaxial, with the principle axis 14i, or optical axis, of the lens 14f. However, in the embodiment illustrated and described here the longitudinal axis 14h of the housing 14e is offset from the principle axis 14i, or optical axis, of the lens 14f. That is, the longitudinal axis 14h of the housing 14e is spaced parallel from the principle axis 14i, or optical axis, of the lens 14f. In this arrangement, the longitudinal axis 14h of the housing 14e is parallel to the principle axis 14i, or optical axis, of the lens 14f, but offset therefrom, i.e. separated by a lateral distance D, as illustrated in Fig. 6a.

As stated above, the longitudinal axis 14h of the housing 14e is the centre io of rotation of the housing 14e, or the rotational axis of the housing 14e.

The principle axis 14i, or optical axis, of the lens 14f is the off-centre axis of the optical fibre collimator 14. In this arrangement, as the housing 14e rotates, the principle axis 14i, or optical axis, of the lens 14f translates in a direction which is perpendicular to the longitudinal axis 14h of the housing

14e. Continued and repeated rotation of the housing 14e causes the principle axis 14i, or optical axis, of the lens 14f to oscillate in a direction which is perpendicular to the longitudinal axis 14h of the housing 14e.

The principle axis 14i, or optical axis, of the lens 14f may function as a cam as the housing 14e is rotated.

As illustrated in Figs. 1 to 4c and 6c, the housing 14e is a cylindrical member with a circular lateral cross section. However, it should be appreciated that the housing 14e may have other shapes with other lateral cross sections. By way of example only, the housing may have a polygon25 shaped lateral cross section, an irregular polygon-shaped lateral cross section (Fig. 6c), a rectangular-shaped lateral cross section, a D-shaped lateral cross section, or a octagon-shaped lateral cross section (Fig. 6b).

Where the apparatus 10 is of the version where the collimated light input device 12 and the collimated light output device 14 is a single component, the standard/auto collimator 15 comprises a housing 15a and a lens 15b (Fig. 5). The standard/auto collimator 15 is configured such that collimated light travelling into the lens 15b is coupled by the lens 15b into the optical fibre 13a of the collimated light input collimator 13.

The housing 15a is a longitudinal member with a longitudinal axis 15c.

The longitudinal axis 15c is an axis of rotation. The longitudinal axis 15c may also be an axis of symmetry, a central axis, or a mechanical axis.

io The longitudinal axis 15c of the housing 15a may coincide, or be coaxial, with the principle axis 15d, or optical axis, of the lens 15b. However, in the embodiment illustrated and described here the longitudinal axis 15c of the housing 15a is offset from the principle axis 15d, or optical axis, of the lens 15b. That is, the longitudinal axis 15c of the housing 15a is spaced parallel from the principle axis 15d, or optical axis, of the lens 15b. In this arrangement, the longitudinal axis 15c of the housing 15a is parallel to the principle axis 15d, or optical axis, of the lens 15b, but offset therefrom, i.e. separated by a lateral distance D, as illustrated in Fig. 5.

As stated above, the longitudinal axis 15c of the housing 15a is the centre of rotation of the housing 15a, or the rotational axis of the housing 15a.

The principle axis 15d, or optical axis, of the lens 15b is the off-centre axis of the standard/auto collimator 15. In this arrangement, as the housing 15a rotates, the principle axis 15d, or optical axis, of the lens 15b translates in a direction which is perpendicular to the longitudinal axis 15c of the housing 15a. Continued and repeated rotation of the housing 15a causes the principle axis 15d, or optical axis, of the lens 15b to oscillate in a direction which is perpendicular to the longitudinal axis 15c of the housing 15a. The principle axis 15d, or optical axis, of the lens 15b may function as a cam as the housing 15a is rotated.

As illustrated in Fig. 5, the housing 15a is a cylindrical member with a circular lateral cross section. However, it should be appreciated that the housing 15a may have other shapes with other lateral cross sections. By way of example only, the housing may have a polygon-shaped lateral cross section, an irregular polygon-shaped lateral cross section (Fig. 6c), a rectangular-shaped lateral cross section, a D-shaped lateral cross section, or an octagon-shaped lateral cross section (Fig. 6b). [Note the reference signs for the standard/auto collimator 15 have been omitted from these io figures for clarity.]

As illustrated in Figs. 1 through 4c, the collimated light attenuation apparatus 10 includes a base plate 32. The baseplate 32 provides support to the components of the apparatus 10. The collimated light input device 12 and the collimated light output device 14 are secured to the base plate 32. The collimated light input device 12 and the collimated light output device 14 may be secured to the base plate 32 with a polyepoxide, epoxy resin, or the like. Similarly, where the apparatus includes the standard/auto collimator 15, the standard/auto collimator 15 is secured to the base plate with a polyepoxide, epoxy resin, or the like. In the embodiment illustrated and described here the base plate 32 includes ceramic pads 34 and the collimated light input device 12, the collimated light output device 14 or standard/auto collimator 15 are secured to the ceramic pads 34 with a polyepoxide, epoxy resin, or the like.

The collimated light reflection component 18 is configured to reflect collimated light from the collimated light input device 12 to the collimated light output device 14, or standard/auto collimator 15. The collimated light reflection component 18 may be a retroreflector.

The collimated light reflection component 18 is configured to be moveable with respect to the collimated light input device 12 and the collimated light output device 14. That is, the distance that the collimated light reflection component 18 is located from the collimated light input device 12 and the collimated light output device 14 may be varied.

The collimated light attenuation apparatus 10 further comprises a chassis 36. The chassis 36 provides support to the collimated light reflection component 18 and the base plate 32.

io

The collimated light attenuation apparatus 10 further comprises a carriage 38 which is moveable with respect to the collimated light input device 12 and the collimated light output device 14. Again, the distance that the carriage 38 is located from the collimated light input device 12 and the collimated light output device 14 may be varied. The carriage 38 supports the collimated light reflection component 18. The collimated light reflection component 18 may be secured to the carriage 38 by bonding, or the like.

As described above, the collimated light attenuation apparatus 10 further comprises a motor 20. The motor 20 is operable to move the carriage 38 via a screw drive arrangement 42. The motor 20 may be a stepper motor. The carriage 38 is mounted to a screw drive arrangement, such that rotation of the screw member 44 therein by the motor 20 causes translation of the carriage 38 along the chassis 36.

Varying the distance between the collimated light reflection component 18 and the collimated light input device 12 and the collimated light output device 14 varies the length of the optical light path 22.

As best illustrated in Fig. 1, the chassis 36 comprises travel limiting abutments 46. The travel limiting abutments 46 are configured to control the minimum and maximum distance of the collimated light reflection component 18 from the collimated light input device 12 and the collimated light output device 14. The travel limiting abutments 46 may be, or include, optical switches, the operation of the motor 20 and thus control the minimum and maximum distance of the collimated light reflection component 18 from the collimated light input device 12 and the collimated light output device 14.

io

By way of example only, the apparatus 10 may be a collimated light variable optical delay line with the following performance characteristics:

Wavelength Range	850nm - 1380nm
Optical Input Power	>10mW Continuous Exposure
Optical Path Variation	0 - 120mm
Optical Delay Range	0 to 1067ps
Travel Speed	30mm/s max
Travel Resolution	5pm
Optical Delay Resolution	0.03ps
Double Pass Optical Insertion Loss	<1.5dB @ 1310nm
Double Pass Insertion Loss Variation	<±0.5dB Entire Travel Range
Double Pass Wavelength Dependent Loss	<±0.3dB 1220- 1380nm
Temperature Dependent Insertion Loss	<0.5dB 15-50°C
Return Loss	>55dB
Operating Temperature Range	+10°C to +50°C

As described above, in use, light travelling along fibre optic cable 12a is collimated by the collimated light input device 12 and launched into the free space in the apparatus 10. Assuming the collimated light attenuation device 16 is set at the first minimum attenuation position (Figs. 2a to 2c), the collimated light beam 12b proceeds along the optical path 22 to the collimated light reflection component 18, which reflects the collimated light back towards the collimated light output device 14. The components of the apparatus 10 are arranged such that returned collimated light avoids the collimated light attenuation device 16. The collimated light beam 12b io is then received by the collimated light output device 14 and coupled into the fibre optic cable 14a.

As described above, the position of the collimated light reflection component 18 is set to provide the optical delay required from the apparatus 10. Furthermore, the position of the collimated light attenuation device 16 is set to provide the attenuation of the collimated light required by the apparatus 10.

Prior to use of the apparatus 10, the components of the apparatus 10, including the collimated light input device 12 and collimated light output device 14, are positioned to correct the height and parallelism of the collimated light beams entering and leaving the apparatus 10. For the collimated light input device 12 and collimated light output device 14, this includes rotating the housings 12e, 14e thereof to adjust the height and position of the principle axes 12h, 14h of the lenses 12f, 14f, as described above. Once the adjustment of the collimated light input device 12 and collimated light output device 14 has been performed they are fixed to the baseplate 32 (or ceramic pads 34) by a polyepoxide, epoxy resin, or the like.

Providing a collimated light attenuation device 16 as described above ensures that the collimated light beam 12b can be fully attenuated, even if the exact position of the beam is not well defined. The large planar area of the attenuation member 16 ensures that all collimated light is incident on the attenuation member 16 when it is in the second maximum attenuation position.

Furthermore, providing an attenuation device 16 with a housing 16d, attenuation member 16, screw member 16 and adjustment screw 26 as io described above, ensures that full attenuation of the collimated light beam 12b may be achieved without any component of the attenuation device 16 protruding out of the apparatus 10. This is because the screw member 24 is rotatably supported by the housing 16d.

Also, providing collimated light fibre collimators 12,14 where the longitudinal axis 12h, 14h of the housing 12e, 14e is offset from the principle axis 12i, 14i, or optical axis, of the lens 12f, 14f allows the height of the principle axis 12i, 14i to be adjusted by rotating the housing 12e,

14e. This allows very accurate alignment of the optical path 22 of the apparatus 10. Furthermore, this arrangement of collimated light fibre collimators 12, 14 allows the alignment of the components of the apparatus 10 to be set up before fixing the fibre collimators 12, 14 in position. This removes the need to assemble the apparatus, test the alignment of the components, disassemble the apparatus, adjust the position of the components, reassemble the apparatus and test the apparatus. Removing the need to carry out these steps saves a large amount of time.

Furthermore, aligning the collimated light beam to the optical axis of a passively aligned critically component and simultaneously minimising the distance between the collimator housing 12e and the base plate 32 provides stable bonding of the same.

Modifications and improvements may be made to the above without 5 departing from the scope of the present invention. For example, although the apparatus 10 has been illustrated and described above as including a collimated light input device 12 and a separate collimated light output device 14, it should be appreciated that the collimated light input device and the collimated light output device may be the same component, with a io standard/auto collimator used to direct the returned light back into the collimated light input/output device.

Furthermore, it should be appreciated that the collimated light input device 12 and a separate collimated light output device 14 may be identical.

Claims

1. A collimated light attenuation apparatus comprising:

a collimated light input device;

a collimated light output device; and a collimated light attenuation device located in the optical light path between the collimated light input device and the collimated light output device, wherein the collimated light attenuation device is configured to be moveable between a first minimum attenuation position and a second maximum attenuation position, wherein the collimated light attenuation device is configured to be translatable between the first minimum attenuation position and the second maximum attenuation position.

2. The apparatus of claim 1, wherein the collimated light attenuation device is arranged to be translatable in a direction which is perpendicular to the optical light path.

3. The apparatus of claim 1 or claim 2, wherein the collimated light attenuation member includes a planar collimated light attenuating surface.

4. The apparatus of claim 3, wherein the collimated light attenuating surface is perpendicular to the optical light path, or offset from the optical light path.

5. The apparatus of claim 3 or claim 4, wherein the collimated light attenuating surface has an area that is at least the same size as the largest diameter of a collimated light from the collimated light input device.

6. The apparatus of any of claims 3 to 5, wherein the collimated light attenuating surface may have a collimated light beam engaging edge, the edge being linear.

7. The apparatus of claim 6, wherein, in use, a collimated light beam from the collimated light input device is substantially circular with a horizontal and a vertical axis, and the collimated light beam engaging edge is arranged to be parallel, or offset, to the vertical axis of the collimated light beam.

8. The apparatus of any preceding claim, wherein the collimated light attenuation member includes a threaded through bore, the threaded bore being configured to engage with a screw member, the screw member being configured to screw into and out of the threaded bore of the collimated light attenuation member.

9. The apparatus of claim 8, wherein threaded through bore and screw member are arranged perpendicularly to the optical light path.

10. The apparatus of claim 8 or claim 9, wherein the collimated light attenuation device further includes a housing member, the housing member being configured to provide support to the collimated light attenuation member and the screw member.

11. The apparatus of claim 10, wherein the housing member is configured to receive and rotatably support the screw member.

12. The apparatus of claim 10 or claim 11, wherein the housing member includes a collimated light attenuation member receiving portion, the receiving portion being configured to receive the collimated light attenuation member and to guide the member between the first minimum attenuation position and the second maximum attenuation position.

13. The apparatus of claim 12, wherein the collimated light attenuation member receiving portion is configured to allow translation of the collimated light attenuation member in a direction perpendicular to the optical light path and prevent translation of the collimated light attenuation member in a direction parallel to the optical light path.

14. The apparatus of claim 12 or claim 13, wherein the collimated light attenuation member receiving portion includes one or more abutment, or stop, members, the abutment, or stop, members being configured to limit the travel of the collimated light attenuation member.

15. The apparatus of any of claims 8 to 14, wherein the collimated light attenuation device includes an adjustment screw, the adjustment screw being configured to operate the screw member.

16. The apparatus of any of claims 8 to 15, wherein the collimated light attenuation member, collimated light attenuation member receiving portion and screw member are configured such that, upon rotation of the screw member, the collimated light attenuation member translates along the track member with respect to the housing member.

17. The apparatus of any of claims 8 to 16, wherein the collimated light attenuation device further includes a biasing device located between the collimated light attenuation member and the housing member, the biasing device being configured to exert a bias force on the collimated light attenuation member to bias the collimated light attenuation member towards the second maximum attenuation position.

18. The apparatus of any preceding claim, wherein the collimated light input device is an optical fibre collimator having a housing, a lens, an optical fibre ferrule and an optical fibre.

19. The apparatus of claim 18, wherein the optical fibre, is secured within the fibre ferrule, the fibre ferrule is secured within the housing and the lens is secured within the housing.

20. The apparatus of claim 18 or claim 19, wherein the housing has a longitudinal member having a longitudinal axis, the longitudinal axis being an axis of rotation, an axis of symmetry, a central axis, or a central mechanical axis.

21. The apparatus of any of claims 18 to 20, wherein at least a portion of the optical fibre within the housing is configured such that it coincides, or is coaxial, with the principle axis, or optical axis, of the lens.

22. The apparatus of claim 21, wherein the longitudinal axis of the housing is offset, or spaced parallel, from the principle axis, or optical axis, of the lens.

23. The apparatus of any of claims 18 to 22, wherein the housing has a circular, polygon-shaped, irregular polygon-shaped, rectangular-shaped, D-shaped, or octagon-shaped lateral cross section.

24. The apparatus of any preceding claim, wherein the collimated light output device is an optical fibre collimator having a housing, a lens, an optical fibre ferrule and an optical fibre.

25. The apparatus of claim 24, wherein the optical fibre, is secured within the fibre ferrule, the fibre ferrule is secured within the housing and the lens is secured within the housing.

26. The apparatus of claim 24 or claim 25, wherein the housing has a longitudinal member having a longitudinal axis, the longitudinal axis being an axis of rotation, an axis of symmetry, a central axis, or a central mechanical axis.

27. The apparatus of any of claims 24 to 26, wherein at least a portion of the optical fibre within the housing is configured such that it coincides, or is coaxial, with the principle axis, or optical axis, of the lens.

28. The apparatus of claim 27, wherein the longitudinal axis of the housing is offset, or spaced parallel, from the principle axis, or optical axis, of the lens.

29. The apparatus of any of claims 24 to 28, wherein the housing has a circular, polygon-shaped, irregular polygon-shaped, rectangular-shaped, D-shaped, or octagon-shaped lateral cross section.

30. The apparatus of any preceding claim, wherein the collimated light attenuation apparatus further comprises a moveable collimated light reflection component, the moveable collimated light reflection component being configured to reflect collimated light from the collimated light input device to the collimated light output device.

31. A collimated light attenuation device comprising:

a collimated light attenuating member; a screw member; and a housing member, wherein the collimated light attenuating member includes a threaded bore, the threaded bore configured to receive and engage with the screw member, wherein the housing member is configured to provide support to the collimated light attenuating member and the screw member, wherein the housing member is arranged to permit movement of the collimated light attenuating member between a first position on the housing member and a second position on the housing member upon rotation of the screw member.

32. A collimated light variable optical delay line comprising: a collimated light input device;

a collimated light output device;

a moveable collimated light reflection component, the collimated light reflection component being configured to reflect collimated light from the collimated light input device to the collimated light output device; and a collimated light attenuation apparatus located in the optical light path between the collimated light input device and the collimated light output device, wherein the collimated light attenuation device is configured to be moveable between a first minimum attenuation position and a second maximum attenuation position, wherein the collimated light attenuation device is configured to be translatable between the first minimum attenuation position and the second maximum attenuation position.

33. A method of assembling a collimated light attenuation apparatus comprising the steps of:

providing:

a base portion;

34. An optical fibre collimator comprising:

a housing: a lens;

an optical fibre ferrule; and an optical fibre,

5 wherein the optical fibre is secured to the optical fibre ferrule and the lens and the optical fibre ferrule are secured to the housing, and wherein the housing has a longitudinal rotational axis and the lens has a principle axis, and wherein the longitudinal rotational axis of the housing and the principle 10 axis of the lens are offset from one another.

35. A collimated light variable optical delay line comprising:

a collimated light input device and a collimated light output device, wherein at least one of the collimated light input device and 15 collimated light output device is an optical fibre collimator comprising a housing, a lens, an optical fibre ferrule and an optical fibre, and wherein the lens, and optical fibre ferrule are secured to the housing, and

20 wherein the housing has a longitudinal rotational axis and the lens has a principle axis, and wherein the longitudinal rotational axis of the housing and the principle axis of the lens are offset from one another; and a moveable collimated light reflection component, the collimated 25 light reflection component being configured to reflect collimated light from the collimated light input device to the collimated light output device.

Intellectual

Property

Office

Application No: GB1702415.9 Examiner: Mr Chris Davidson