Connection method and connecting structure for photonic crystal fiber
A connection method for a photonic crystal fiber for connecting the photonic crystal fiber and a fiber to be connected, the photonic crystal fiber including a cladding region having a number of microholes and a core region having a same refractive index as that of the cladding region, includes the steps of: abutting respective end faces of the photonic crystal fiber and the fiber to be connected each other; after the abutting, performing a main discharge in which an abutted portion is heated by an electric discharge under a first condition; and after the main discharge, performing an additional discharge in which the connection portion is heated by an electric discharge at least once under a second condition to increase a splice strength.
1. A connection method for connecting a photonic crystal fiber, comprising a cladding region having a number of microholes and a core region having a same refractive index as that of the cladding region, with a second fiber, the method comprising:
abutting a first end face of the photonic crystal fiber and a first end face of the second fiber;
after the abutting, performing a main discharge in which the abutted ends are heated by an electric discharge; and
after the main discharge, performing a second discharge in which the abutted ends are heated by a second electric discharge to increase a connection strength therebetween.
2. The connection method according to claim 1 , wherein the main discharge is performed under a first condition; and the second discharge is performed under a second condition different from the first.
3. The connection method according to claim 1 , wherein a duration of the main discharge is 500 msec or shorter.
4. The connection method according to claim 1 , wherein the second discharge comprises an intermittent discharge in which the electric discharge has an ON duration and an OFF duration.
5. The connection method according to claim 4 , wherein the ON duration is shorter than a duration of the main discharge.
6. The connection method according to claim 4 , wherein the OFF duration is one half to twice of the ON duration.
7. The connection method according to claim 4 , wherein a duration of the second discharge is equal to or longer than a total duration of the ON duration and the OFF duration.
8. The connection method according to claim 1 , wherein the second discharge comprises an intermittent discharge in which the electric discharge has a plurality of ON durations and a plurality of OFF durations.
9. The connection method according to claim 8 , wherein the ON durations are each shorter than a duration of the main discharge.
10. The connection method according to claim 8 , wherein the OFF durations are one half to twice of the respective ON durations.
11. The connection method according to claim 8 , wherein a duration of the second discharge is equal to or longer than a total duration of the plurality of ON durations and the plurality of OFF durations.
12. The connecting method according to claim 1 , wherein:
the abutted ends form a fusion-spliced portion;
a splice loss in the fusion-spliced portion is 0.4 dB or lower; and
a splice strength in the fusion-spliced portion is 0.5 kgf or higher.
13. The connecting method according to claim 12 , wherein the splice loss in the fusion-spliced portion is 0.4 dB or lower in a wavelength band of between 1.25 and 1.65 μm.
14. The connecting method according to claim 1 , wherein the main discharge and second discharge are discrete in time.