Patent ID: 11966079
Assignee: HITACHI ENERGY LTD
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 0:
1. A spliced optical fiber comprising a first and a second polarization-maintaining optical fiber connected to one another at one of their ends by splicing, thereby forming a splice at their connection point, and a protection tube arranged around the spliced optical fiber and surrounding at least an uncoated section of the spliced optical fiber which includes the splice, a first end and a second end of the protection tube sealed to the spliced optical fiber by a first and a second sealing arrangement for protecting the splice against mechanical stress and/or moisture,
the protection tube having such a length that an uncoated section of the spliced optical fiber comprising the splice and a coated section of the spliced optical fiber at each end of the uncoated section are arranged inside the protection tube,
a first distance from the first end of the protection tube and/or from the first sealing arrangement to a position of the splice and a second distance from the position of the splice to the second end of the protection tube and/or to the second sealing arrangement being greater than or equal to a predefined minimum distance Lm, the minimum distance Lm satisfying the following equation:

4√{square root over (X0Xs)}A(Lm)=Xm 

X0 being a maximum guaranteed polarization extinction ratio of the splice, Xs being a maximum guaranteed polarization extinction ratio at the sealed ends of the protection tube, A(L) being a coherence function of a length of the polarization-maintaining fiber and a Fourier transform of an optical power spectrum, and Xm being a predetermined maximum allowable polarization extinction ratio variation.