Coiled optical assembly and fabricating method for the same

Abstract

After a wide-band DCF is wound around a bobbin to form an optical fiber coil 32, the latter is removed from the bobbin and placed into a bundle state (the state where the increase in transmission loss in the wavelength band of 1.55 μm caused by distortions in winding is reduced by 0.1 dB/km or more) released from distortions in winding. A resin 42 is used as a coil-tidying member so as to secure the optical fiber coil 32 to a storage case 40 at four positions. Both ends of the optical fiber coil 32 are connected to pigtail fibers at fusion-splicing parts 44, respectively. Even when the storage case 40 is closed with a lid after the optical fiber coil 32 is secured to the storage case 40 with the resin 42, there remain interstices within the bundle of the optical fiber coil 32 and a space between the optical fiber coil 32 and the storage case 40. As a result, even when the optical fiber coil 32 in a bundle state is accommodated in the storage case 40, transmission loss and the like would not increase.

What is claimed is:  
     
         1 . A coiled optical assembly made of a long optical fiber, said coiled optical assembly comprising: 
 an optical fiber coil in which said long optical fiber is formed into a coil and adjusted into a state where the amount of increase in transmission loss in a predetermined wavelength band upon coiling is reduced by 0.1 dB/km or more; and    a storage case accommodating said optical fiber coil.    
     
     
         2 . A coiled optical assembly according to  claim 1 , wherein said long optical fiber has a wavelength dispersion and a wavelength dispersion slope which have polarities opposite to those of the wavelength dispersion and wavelength dispersion slope of an optical fiber constituting a transmission line, respectively, so that said coiled optical assembly functions as a dispersion compensator for reducing a wavelength dispersion in a predetermined wavelength band.  
     
     
         3 . A coiled optical assembly according to  claim 1 , wherein said optical fiber coil has a diameter of 100 mm or less at a smallest portion thereof.  
     
     
         4 . A coiled optical assembly according to  claim 1 , wherein said long optical fiber has, on an outer peripheral surface thereof, a coating layer in which a primary coating layer made of a coating material having a Young's modulus of at least 0.03 kgf/mm 2  but not greater than 0.15 kgf/mm 2  and a secondary coating layer made of a coating material having a Young's modulus of at least 50 kgf/mm 2  but not greater than 100 kgf/mm 2  are laminated.  
     
     
         5 . A coiled optical assembly according to  claim 4 , wherein said coating layer has a thickness of at least 20 μm but not greater than 70 μm.  
     
     
         6 . A coiled optical assembly according to  claim 1 , wherein said long optical fiber has, on an outer peripheral surface thereof, a coating layer made of a coating material having a Young's modulus of at least 1 kgf/mm 2  but not greater than 120 kgf/mm 2 .  
     
     
         7 . A coiled optical assembly according to  claim 6 , wherein said coating layer has a thickness of at least 20 μm but not greater than 70 μm.  
     
     
         8 . A coiled optical assembly according to  claim 1 , wherein said storage case accommodates said long optical fiber in a bundle form.  
     
     
         9 . A coiled optical assembly according to  claim 8 , further comprising a coil-tidying member which secures said optical fiber coil to said storage case, so as to prevent said optical fiber coil from becoming disordered in winding.  
     
     
         10 . A coiled optical assembly according to  claim 9 , wherein said coil-tidying member is formed by a resin which secures said optical fiber coil to said storage case at a plurality of positions.  
     
     
         11 . A coiled optical assembly according to  claim 9 , wherein said coil-tidying member is a cushion material securing said optical fiber coil to said storage case.  
     
     
         12 . A coiled optical assembly according to  claim 8 , further comprising a filler which fills said storage case and secures and holds said optical fiber coil.  
     
     
         13 . A coiled optical assembly according to  claim 12 , wherein said filler is a thermosetting or UV-curable silicon gel having a Young's modulus of 0.05 kg/mm 2  or less upon curing.  
     
     
         14 . A coiled optical assembly according to  claim 12 , wherein said filler is a jelly-like admixture having a high viscosity.  
     
     
         15 . A coiled optical assembly according to  claim 1 , wherein said optical fiber coil is wound around a bobbin.  
     
     
         16 . A coiled optical assembly according to  claim 15 , wherein said bobbin is made of a metal.  
     
     
         17 . A coiled optical assembly according to  claim 15 , wherein said optical fiber coil has a winding pitch set to a value at least twice as large as the diameter of said long optical fiber.  
     
     
         18 . A coiled optical assembly according to  claim 15 , further comprising a coil-tidying member which secures said optical fiber coil to said bobbin, so as to prevent said optical fiber coil from becoming disordered in winding.  
     
     
         19 . A coiled optical assembly according to  claim 18 , wherein said coil-tidying member is formed by a resin which secures said optical fiber coil to said bobbin at a plurality of positions.  
     
     
         20 . A coiled optical assembly according to  claim 18 , wherein said coil-tidying member is a cushion material securing said optical fiber coil to said bobbin.  
     
     
         21 . A coiled optical assembly according to  claim 15 , wherein a cushioning filler fills gaps between turns of the optical fiber constituting said optical fiber coil.  
     
     
         22 . A coiled optical assembly according to  claim 21 , wherein said filler is a thermosetting or UV-curable silicon gel having a Young's modulus of 0.05 kg/mm 2  or less upon curing.  
     
     
         23 . A coiled optical assembly according to  claim 21 , wherein said filler is a jelly-like admixture having a high viscosity.  
     
     
         24 . A fabricating method for a coiled optical assembly made of a long optical fiber, said method comprising: 
 a coil making step of winding said long optical fiber around a bobbin so as to make an optical fiber coil; and    an adjustment step of adjusting said optical fiber into a state where the amount of increase in transmission loss in a predetermined wavelength band upon said coil making step is reduced by 0.1 dB/km or more.    
     
     
         25 . A fabricating method for a coiled optical assembly according to  claim 24 , further comprising a filling step of accommodating said optical fiber coil in a storage case and filling said storage case with a cushioning filler after said adjustment step.  
     
     
         26 . A fabricating method for a coiled optical assembly according to  claim 24 , wherein, in said adjustment step, after said coil making step, said optical fiber coil is held at at least one of temperatures which are lower and higher than the temperature in said coil making step, respectively.  
     
     
         27 . A fabricating method for a coiled optical assembly according to  claim 24 , wherein, in said adjustment step, said bobbin wound with said optical fiber coil is vibrated after said coil making step.  
     
     
         28 . A fabricating method for a coiled optical assembly according to  claim 24 , wherein, in said adjustment step, said optical fiber coil is removed from said bobbin and thus removed optical fiber coil is loosened into a bundle form.  
     
     
         29 . A fabricating method for a coiled optical assembly according to  claim 27 , further comprising a lubricant coating step of coating said bobbin with a lubricant prior to at least one of said coil making step and adjustment step.  
     
     
         30 . A fabricating method for a coiled optical assembly made of a long optical fiber, said method comprising: 
 a coil making step of forming an optical fiber coil by winding said long optical fiber around a bobbin in a state where the amount of increase in transmission loss in a predetermined wavelength band upon winding is reduced by 0.1 dB/km or more.    
     
     
         31 . A fabricating method for a coiled optical assembly according to  claim 30 , wherein, in said coil making step, said long optical fiber is wound around said bobbin in a state where at least one of said long optical fiber and bobbin is maintained at a predetermined temperature not lower than 60° C.  
     
     
         32 . A fabricating method for a coiled optical assembly according to  claim 30 , wherein, in said coil making step, said long optical fiber is wound around said bobbin at a take-up tension of 50 gf or less.  
     
     
         33 . A fabricating method for a coiled optical assembly made of a long optical fiber, said method comprising: 
 a coil making step of winding said long optical fiber around a bobbin so as to make an optical fiber coil; and    a body diameter changing step of substantially reducing, after said coil making step, the diameter of said bobbin from the diameter thereof in said coil making step, so that said optical fiber is adjusted into a state where the amount of increase in transmission loss in a predetermined wavelength band upon coiling is reduced by 0.1 dB/km or more.    
     
     
         34 . A fabricating method for a coiled optical assembly made of a long optical fiber, said method comprising: 
 a filler coating step of coating an outer periphery of a long optical fiber with a cushioning filler; and    a coil making step of winding said long optical fiber, whose outer periphery is coated with said filler, around a bobbin, so as to make an optical fiber coil.    
     
     
         35 . A fabricating method for a coiled optical assembly made of a long optical fiber, said method comprising: 
 a coil making step of coating, simultaneously with winding said long optical fiber around a bobbin, a surface of said bobbin for winding said long optical fiber and thus wound long optical fiber with a cushioning filler, so as to make an optical fiber coil.