|Publication number||USRE39934 E1|
|Application number||US 10/324,028|
|Publication date||Dec 4, 2007|
|Filing date||Dec 20, 2002|
|Priority date||Nov 24, 1998|
|Also published as||CA2288290A1, CA2288290C, US6167185|
|Publication number||10324028, 324028, US RE39934 E1, US RE39934E1, US-E1-RE39934, USRE39934 E1, USRE39934E1|
|Inventors||John O. Smiley, Robert LaFlamme|
|Original Assignee||Jds Uniphase, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (14), Non-Patent Citations (1), Classifications (12), Legal Events (5)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This invention relates to an optical attenuator for attenuating the intensity of a beam of light, and in particular to an optical attenuator that preserves the composition of polarization of a beam of light over a wide range of attenuation.
Between a transmitter and a detector of a fiber optic system, attenuation of the signal strength occurs. The system is designed for a normal amount of signal loss between transmitter and detector. At the detector, the signal strength must be maintained within an appropriate range. The minimum strength is determined by the need for an adequate signal-to-noise ratio. The maximum strength is determined by the need to avoid an overload of the detector.
In U.S. Pat. No. 5,325,459 issued to S. Schmidt in June, 1994 an optical attenuator is disclosed comprising a disk formed from two separate portions, a wedge shaped disk made of a light absorbing material affixed to a wedge shaped transparent disk. For adjusting different attenuations, the disk is rotated around an axis by a motor. The attenuator needs a complex setup to compensate for refraction and resulting beam deviations. The compensations ensure that the beam of light is coupled into the optical fiber at any angular orientation of the attenuator disk. As such, the device is expensive and prone to reliability problems.
A well known alternative to the complex solution disclosed in U.S. Pat. No. 5,325,459 is the use of an opaque straight edge disposed within the optical path of a collimated beam of light. Unfortunately, using this device for attenuating a beam of light results in a change of the polarization composition of the beam of light. This is an undesirable effect when used in an optical fibre network. Since polarization components of light within the system are often not known it is a disadvantage to have polarization dependent attenuation.
It would be advantageous to provide an attenuator that maintains the polarization composition of a beam of light.
It is an object of the invention to provide an optical attenuator for attenuating the intensity of a beam of light that preserves the polarization composition of a beam of light over a wide range of attenuation.
It is further an object of the invention to provide an optical attenuator that is easily implemented in a fiber optic network.
According to the invention a method of attenuating a beam of light having a circular cross-section is provided. The method comprises the step of disposing a member within the beam of light, the intersection of the member and the beam of light defining a region having two substantially equal sides defining an angle other than 0 degrees and 180 degrees therebetween the two sides having a central line of symmetry coincident with a line of symmetry through the centre of the circle, the angle moving along the line of symmetry.
According to the invention an optical attenuator for attenuating a beam of light having a circular cross-section is provided. The optical attenuator comprises:
Exemplary embodiments of the invention will now be described in conjunction with the drawings, in which:
Alternatively, the attenuator comprises an opaque cone within a transparent body. For example, such an attenuator is realised by immersing a cone made of laminated glass in a transparent fluid, the glass and the fluid having matching refractive indices. During a cooling process the fluid solidifies and retains the cone at a predetermined location within the solidified fluid.
Further alternatively, the attenuator comprises a transparent body having a conic indention, wherein the surface of the body defining the indention is covered with a layer of opaque or light absorbing material.
Preferably, the cone 18 comprises an angle of 90 degrees. In order to attenuate the light within the beam of light while maintaining the polarization composition the cone is moved into the beam of light such that the point of the cone moves along a diameter of a cross section of the beam of light and the side of the cone that is illuminated by the beam of light is substantially symmetrical about the diameter. In this way, approximately an equal amount of light of each orthogonal polarization is blocked or attenuated.
The attenuator according to the invention is advantageous compared with prior art devices such as a straight edge because the attenuated beam of light has substantially a same polarization composition as the collimated beam of light.
In another embodiment according to the invention the beam of light 16 is attenuated using a wedge shaped edge. Preferably, the edge comprises at least an outer layer of light absorbing material in order to prevent light reflected from the edge from interfering with the incoming beam of light 16. Preferably the wedge is substantially flat, thereby allowing it to be moved into and out of a narrow gap.
Optionally, the attenuator comprises a wedge shaped body of light absorbing material.
Alternatively, the attenuator comprises a body of light absorbing material having a wedge shaped opening.
In another embodiment according to the invention the beam of light 16 is reflected by the reflective surface 25 onto an output lens 14, different from the input lens 12.
Optionally, the cone 18 is moved in another fashion such that the tip of the cone is within the optical path of the collimated beam of light 16 and the portion of the beam of light 16 blocked by the cone is altered. Referring to
A beam attenuator according to the invention is defined herein and in the claims that follow to comprise an object or a portion of an object, the object or the portion of an object for attenuating light. For example, when a rectangular glass plate is provided with an opaque arrow head thereon, the beam attenuator refers to the opaque arrowhead.
Of course, numerous other embodiments may be envisaged without departing from the spirit and scope of the claimed invention.
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|CA2202308A1||Apr 10, 1997||Oct 19, 1997||Fujikura Ltd||Optical waveguide grating and production method therefor|
|JPH04317009A *||Title not available|
|JPS5573002A *||Title not available|
|U.S. Classification||385/140, 385/34, 385/25, 385/36|
|International Classification||G02B6/00, G02B6/26, G02B6/35|
|Cooperative Classification||G02B6/3594, G02B6/353, G02B6/266|
|European Classification||G02B6/26C2, G02B6/35E8|
|Jun 26, 2008||FPAY||Fee payment|
Year of fee payment: 8
|Jul 7, 2008||REMI||Maintenance fee reminder mailed|
|Jun 26, 2012||FPAY||Fee payment|
Year of fee payment: 12
|Jul 9, 2015||AS||Assignment|
Owner name: JDS UNIPHASE CORPORATION, CALIFORNIA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:JDS UNIPHASE INC.;REEL/FRAME:036087/0320
Effective date: 20150626
|Aug 21, 2015||AS||Assignment|
Owner name: LUMENTUM OPERATIONS LLC, CALIFORNIA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:JDS UNIPHASE CORPORATION;REEL/FRAME:036420/0340
Effective date: 20150731