Optical fiber thermal compensation device

Abstract

An optical filter having at least one optical fiber component and a thermal compensation device which includes a first, second and third member in which the thermal compensation device has a first and a second fixing point, the first, second and third members are made from materials having first, second and third thermal expansion coefficients, the optical fiber component is attached to the thermal compensation device at the first and the second fixing points thus defining a composite thermal expansion. The optical filter is such that the composite thermal expansion compensates for thermal behavior of the optical fiber component.

We claim:  
     
         1 . An optical filter, comprising at least one optical fiber component and a thermal compensation device comprising a first member, a second member and a third member, and wherein: 
 the thermal compensation device has a first and a second fixing point, the first, second and third members are made from materials having respective first, second and third thermal expansion coefficients, the optical fiber component is attached to the thermal compensation device at the first and the second fixing points to thereby define a composite thermal expansion, and the optical filter is configured such that the composite thermal expansion compensates for the thermal behavior of the optical fiber component; and    the first, second and third members are configured such that the thermal compensation device experiences a substantially zero bending moment induced by strain in the optical fiber component.    
     
     
         2 . The optical filter of  claim 1 , and wherein the optical fiber component is selected from the group comprising a filter, a fiber Bragg grating, a multiplexer grating, a demultiplexer grating, an add grating, a drop grating, a dispersion compensator, an optical gain shaper, a wavelength locker, a sensor grating, a distributed feedback fiber laser and a fiber laser.  
     
     
         3 . The optical filter of  claim 1 , and further wherein the first, second and third members share a common central longitudinal axis which is defined by the optical fiber component.  
     
     
         4 . The optical filter of  claim 3 , and further wherein the first, second and third members are circular in cross section.  
     
     
         5 . The optical filter of  claim 1 , and wherein the optical filter is characterized by an operating wavelength having a desired wavelength.  
     
     
         6 . The optical filter of  claim 1 , and wherein the first and third thermal expansion coefficients are substantially equal.  
     
     
         7 . The optical filter of  claim 1 , and wherein the second thermal expansion coefficient is larger than the first and third thermal expansion coefficients.  
     
     
         8 . The optical filter of  claim 1 , and wherein the composite thermal expansion is negative.  
     
     
         9 . The optical filter of  claim 1 , and wherein the composite thermal expansion is in the range −4×10 −6  to −15×10 −6 .  
     
     
         10 . The optical filter of  claim 1 , and wherein at least one of the first, second and third members is a cylinder.  
     
     
         11 . The optical filter of  claim 10 , and wherein the second cylinder and the third cylinder are joined with a first fixing means to form an interim assembly, and wherein the fixing means is selected from the group comprising a laser weld, a metal solder, a Eutectic, a glass solder, an adhesive, an epoxy, a thermally cured adhesive and a UV cured adhesive.  
     
     
         12 . The optical filter of  claim 11 , and wherein the first cylinder is joined to the interim assembly using a second fixing means.  
     
     
         13 . The optical filter of  claim 12 , and wherein the second fixing means is a laser weld.  
     
     
         14 . The optical filter of  claim 12 , and wherein the operating wavelength is tuned to the desired wavelength while joining the first cylinder to the interim assembly.  
     
     
         15 . The optical filter of  claim 1 , and wherein the first, second and third members are cylinders.  
     
     
         16 . The optical filter of  claim 1 , and wherein the thermal compensation device and the optical component are each defined by a respective length, and further wherein the length of the thermal compensation device is greater than or equal to the length of the optical component, and the length of the thermal compensation device is independent of the length of the optical component.  
     
     
         17 . The optical filter of  claim 1 , and wherein the first and the second fixing points are separated by a distance of a longitudinal length, and further wherein the length of the thermal compensation device is less than 20 mm longer than the longitudinal length separating the first and the second fixing points.  
     
     
         18 . The optical filter of  claim 1 , and further comprising a plurality of optical fiber components, and the thermal compensation device has plurality of first fixing points and a plurality of second fixing points, and wherein each optical fiber component is attached to the thermal compensation device at respective first and second fixing point to thereby define a composite thermal expansion.  
     
     
         19 . An optical filter, comprising at least one optical fiber component and a thermal compensation device comprising a first member, a second member and a third member, and wherein: 
 the thermal compensation device has a first and a second fixing point, the first, second and third members are made from materials having respective first, second and third thermal expansion coefficients, the optical fiber component is attached to the thermal compensation device at the first and the second fixing points to thereby define a composite thermal expansion, and the optical filter is configured such that the composite thermal expansion compensates for the thermal behavior of the optical fiber component; and    the optical fiber component is attached to the first and the second fixing points using a glass solder.    
     
     
         20 . The optical filter of  claim 19 , and wherein the operating wavelength is tuned to the desired wavelength while the glass solder is flowed.  
     
     
         21 . The optical filter of  claim 1 , and wherein the optical fiber component is attached to the thermal compensation device at the first and the second fixing points using a glass solder which forms a hermetic seal.  
     
     
         22 . A method of manufacturing an optical filter wherein the optical fiber component is characterized by an operating wavelength of a selected wavelength, and wherein the optical filter comprises an optical fiber component attached to a thermal compensation device at first and second fixing points, the method comprising: 
 i. inserting the optical fiber component into the thermal compensation device;    ii. applying strain to the optical fiber component;    iii. flowing glass solder to attach the optical fiber component to the thermal compensation device at the first and the second fixing points;    iv. , measuring the operating wavelength of the optical fiber component;    v. adjusting the strain applied to the optical fiber component to tune the operating wavelength to the selected wavelength; and    vi. allowing the glass solder to solidify;    wherein the step of measuring the operating wavelength of the optical fiber component is carried out prior to adjusting the strain applied to the optical fiber component to tune the operating wavelength, and the step of allowing the glass solder to solidify is carried out after adjusting the strain applied to the optical fiber component to tune the operating wavelength.    
     
     
         23 . The method of  claim 22 , and further comprising adjusting the strain while flowing the glass solder.  
     
     
         24 . The method of  claim 22 , and wherein the optical fiber component is attached to the first fixing point prior to tuning the operating wavelength to the selected wavelength.  
     
     
         25 . The method of  claim 23 , and further comprising measuring and feeding back the operating wavelength while flowing the glass solder in order to tune the operating wavelength to the selected wavelength.  
     
     
         26 . The method of  claim 25 , and wherein the measuring and feeding back of the operating wavelength while flowing the glass solder are carried out more than once.  
     
     
         27 . The method of  claim 25 , and wherein the measuring and feeding back of the operating wavelength while flowing the glass solder is continued until the operating wavelength is within a desired amount of the desired wavelength.  
     
     
         28 . The method of  claim 26 , and wherein the desired amount of the desired wavelength is one of +/−10 pm, +/−5 pm, +/−2 pm, or +/−1 pm.  
     
     
         29 . The method of  claim 22 , and wherein the glass solder is flowed using a heating method selected from the group comprising induction heating, an electric current heating method, resistance welding, a hot gas method, a hot glass injection method, and a direct heating method.  
     
     
         30 . The method of  claim 29 , and further comprising: 
 i. measuring the operating wavelength of the optical fiber component; and    ii. flowing the glass solder on either the first or the second fixing point while adjusting the strain applied to the optical fiber component to tune the operating wavelength to the desired wavelength.    
     
     
         31 . The method of  claim 30 , and further comprising, prior to measuring the operating wavelength and flowing the glass solder, thermally annealing the optical filter.  
     
     
         32 . The method of  claim 22 , and wherein the thermal compensation device comprises a first member, a second member, and a third member, and wherein the thermal compensation device is formed by laser welding the first, the second and the third members together.  
     
     
         33 . The method of  claim 22 , and wherein the thermal compensation device further comprises third and fourth fixing points outside of the first and the second fixing points, and wherein the method further comprises attaching the optical fiber component to the third and the fourth fixing points to provide strain relief.  
     
     
         34 . The method of  claim 33 , and wherein the optical fiber component is bent between the first and third fixing points.  
     
     
         35 . The method of  claim 22 , and further comprising injecting a fluid into the thermal compensation device.  
     
     
         36 . The method of  claim 35 , and wherein the fluid is selected from the group comprising an oil, a grease, a gel, an ink, a liquid metal, and a heat-sinking compound.  
     
     
         37 . The method of  claim 22 , and wherein the optical fiber component is a distributed feedback fiber laser, and the thermal compensation device further comprises a heat sink.  
     
     
         38 . The method of  claim 37 , and wherein the heat sink is laser welded to the first member.  
     
     
         39 . A method of manufacturing an optical filter wherein the optical filter comprises an optical fiber component attached to a thermal compensation device at first and second fixing points, and wherein the thermal compensation device comprises first, second and third members, the method comprising sequentially: 
 i. laser welding the first and second members together to form an interim assembly,    ii. attaching the optical fiber component to one of the interim assembly and the third member,    iii. attaching the optical fiber component to the other one of the interim assembly and the third member,    iv. applying strain to the optical fiber component, and    v. laser welding the third member to the interim assembly.    
     
     
         40 . The method of  claim 39 , and wherein the third member is assembled onto the interim assembly prior to attaching the optical fiber component to either the interim assembly or the third member.  
     
     
         41 . The method of  claim 39 , and wherein the optical fiber component is characterized by an operating wavelength of a selected wavelength, and further comprising, prior to laser welding the third member to the interim assembly: 
 i. measuring the operating wavelength of the optical fiber component; and    ii. adjusting the strain applied to the optical fiber component to tune the operating wavelength to the selected wavelength.    
     
     
         42 . The method of  claim 39 , and wherein the optical fiber component is attached to the thermal compensation device using a glass solder.  
     
     
         43 . The method of  claim 42 , and further comprising measuring and feeding back the operating wavelength while flowing the glass solder in order to tune the operating wavelength to the desired wavelength.  
     
     
         44 . The method of  claim 43 , and wherein the measuring and feeding back of the operating wavelength while flowing the glass solder are carried out more than once.  
     
     
         45 . The method of  claim 42 , and wherein the glass solder is flowed using a heating method selected from the group comprising induction heating, an electric current heating method, resistance welding, a hot gas method, a hot glass injection method, and a direct heating method.  
     
     
         46 . The method of  claim 39 , and wherein the optical fiber component is attached to the thermal compensation device using one of a group comprising an epoxy, an eutectic, an adhesive including a UV-cured adhesive, and an acrylic-based adhesive.  
     
     
         47 . The method of  claim 39 , and wherein the thermal compensation device further comprises third and fourth fixing points outside of the first and the second fixing points, and wherein the method further comprises attaching the optical fiber component to the third and the fourth fixing points to provide strain relief.  
     
     
         48 . The method of  claim 47 , and wherein the optical fiber component is bent between the first and third fixing point.