OPTICAL SIDE INPUT/OUTPUT CIRCUIT AND OPTICAL CONNECTOR
The present invention aims to provide an optical side input/output circuit that has wavelength selectivity and is easily disposed at multiple points in a transmission path, and an optical connector. The optical side input/output circuit 301 includes: a tap portion 10 in which a tap waveguide 53 that outputs light of a higher-order mode from a side surface of an optical fiber 50 is formed, the light of the higher-order mode being of light propagating in the core 51 of the optical fiber 50; and a grating portion 20 that is located in a stage before the tap portion 10 in the propagation direction of the light, and has a grating 21 that converts light of a desired wavelength from a basic mode to the higher-order mode, the grating 21 being formed in the core 51 of the optical fiber 50.
1 . An optical side input/output circuit comprising:
a tap portion in which a tap waveguide that outputs light of a higher-order mode from a side surface of an optical fiber is formed, the light of the higher-order mode being of light propagating in a core of the optical fiber; and
a grating portion that is located in a stage before the tap portion in a propagation direction of the light, and has a grating that converts light of a desired wavelength from a basic mode to the higher-order mode, the grating being formed in the core of the optical fiber.
2 . The optical side input/output circuit according to claim 1 , wherein
the grating portion has a normalized frequency V of 2.4 or higher at the desired wavelength, and
the tap portion satisfies
d t /d c ≥0.24 V− 0.27,
0.33≤ d t /d c ≤0.87,
0.28 V− 0.35≤δ n /( n core −n clad )≤0.03 V+ 1.28, and
α−0.58 V 2+2.65 V− 1.48,
where d t represents a diameter of the tap waveguide, d c represents a diameter of the core of the optical fiber, δn represents a refractive index change amount of the tap waveguide with respect to the optical fiber, n core and n clad represent a refractive index of the core of the optical fiber and a refractive index of a cladding, respectively, and α represents an angle (°) formed by the core of the optical fiber and the tap waveguide.
3 . The optical side input/output circuit according to claim 1 , wherein a refractive index of a core of the grating portion is higher than a refractive index of a core of the tap portion.
4 . The optical side input/output circuit according to 1 , wherein a plurality of sets of the tap portion and the grating portion is continuously arranged in the optical fiber.
5 . The optical side input/output circuit according to claim 1 , further comprising a light receiver that is disposed on the side surface of the optical fiber, and receives the light output from the tap portion.
6 . An optical connector comprising the optical side input/output circuit according to claim 1 .