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

Claim 18:
19. A method comprising:
connecting a first end of a first polarization-maintaining optical fiber and a second end of a second polarization-maintaining optical fiber by a splice with a maximum polarization extinction ratio of X0;
arranging a protection tube around the spliced optical fiber such that the protection tube surrounds at least an uncoated section of the spliced optical fiber which includes the splice, 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; and
sealing a first end of the protection tube to the spliced optical fiber by a first sealing arrangement and sealing a second end of the protection tube to the spliced optical fiber by a second sealing arrangement, such that:
a maximum polarization extinction ratio of the spliced optical fiber at the first and/or the second sealing arrangement is Xs;
the length of the protection tube is such that 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 are greater than or equal to a predefined minimum distance Lm that satisfies the following equation:

4√{square root over (X0Xs)}A(Lm)=Xm 

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.