Chromatic dispersion compensator and chromatic dispersion compensating optical communication system

Claim 2

A chromatic dispersion compensator comprising: optical signal directing means having first, second and third ports, for directing an optical signal input from one of said ports to another port of said ports; an input transmission path which is connected to said first port; an output transmission path which is connected to said third port; a chirped grating which is connected to said second port; and a dispersion compensating fiber which is connected to at least one of said first, second and third ports, said dispersion compensating fiber and said chirped grating having chromatic dispersion characteristics opposite to the chromatic dispersion characteristics of said input and output transmission paths; wherein the optical signal is incident into said first port from said input transmission path, the optical signals is made to go out to said chirped grating from said second port, the optical signal is incident from said chirped grating to return to said second port, and the optical signal is made to go to said output transmission path from said third port; wherein almost all chromatic dispersion is compensated by the dispersion compensation optical fiber, and wherein the chirped grating is arranged so that only a wavelength-dependent component of the residual chromatic dispersion is compensated by the chirped grating, said chirped grating having a dispersion slope opposite to that of the residual chromatic dispersion and substantially equal in absolute value to the dispersion slope of the wavelength-dependent component of the residual chromatic dispersion.

Claim 3

A chromatic dispersion compensator according to claim 1, further comprising an optical fiber amplifier which is connected to at least one of said first and third ports.

Claim 4

A chromatic dispersion compensator according to claim 1, wherein said optical signal directing means is an optical circulator.

Claim 5

A chromatic dispersion compensator according to claim 3, further comprising an optical fiber amplifier which is connected to at least one of said first and third ports.

Claim 6

A chromatic dispersion compensator according to claim 1, wherein said optical signal directing means is a directional coupler.

Claim 7

A chromatic dispersion compensator according to claim 5, further comprising an optical fiber amplifier which is connected to at least one of said first and third ports.

Claim 8

A chromatic dispersion compensator according to claim 5, wherein said optical signal direction means has a fourth port.

Claim 9

A chromatic dispersion compensator according to claim 7, wherein said fourth port has a nonreflective terminal.

Claim 10

A chromatic dispersion compensator according to claim 1, wherein said chirped grating has a nonreflective terminal.

Claim 11

A chromatic dispersion compensating optical communication system, comprising: a transmission path comprising a 1.31 μm-band single mode fiber; and a chromatic dispersion compensator which is connected to an one of an intermediate and an end portion of said transmission path, said chromatic dispersion compensator comprising: optical signal directing means having a first, second and third ports, for directing an optical signal input from one of said ports to another port of said ports; an input transmission path which is connected to said first port; an output transmission path which is connected to said third port; a chirped grating which is connected to said second port; and a dispersion compensating fiber which is connected to at least one of said first, second and third ports, said dispersion compensating fiber and said chirped grating having chromatic dispersion characteristics opposite to the chromatic dispersion characteristics of said input and output transmission path, said dispersion compensating fiber having negative chromatic dispersion in a wavelength range used; wherein the optical signal is incident into said first port from said input transmission path, the optical signal is made to go out to said chirped grating from said second port, the optical signal is incident from said chirped grating to return to said second port, and the optical signal is made to go to said output transmission path from said third port; wherein almost all chromatic dispersion is compensated by the dispersion compensation optical fiber, and wherein the chirped grating is arranged so that only a wavelength-dependent component of the residual chromatic dispersion is compensated by the chirped grating, said chirped grating having a dispersion slope opposite to that of the residual chromatic dispersion and substantially equal in absolute value to the dispersion slope of the wavelength-dependent component of the residual chromatic dispersion.

Claim 12

A chromatic dispersion compensating optical communication system, comprising: a transmission path comprising a 1.31 μm-band single mode fiber; and a chromatic dispersion compensator which is connected to an one of an intermediate and an end portion of said transmission path, said chromatic dispersion compensator comprising: optical signal directing means having a first, second and third ports, for directing an optical signal input from one of said ports to another port of said ports; an input transmission path which is connected to said first port; an output transmission path which is connected to said third port; a chirped grating which is connected to said second port; and a dispersion compensating fiber which is connected to at least one of said first, second and third ports, said dispersion compensating fiber and said chirped grating having chromatic dispersion characteristics opposite to the chromatic dispersion characteristics of said input and output transmission path, said dispersion compensating fiber having negative chromatic dispersion in a wavelength range used; wherein the optical signal is incident into said first port from said input transmission path, the optical signal is made to go out to said chirped grating from said second port, the optical signal is incident from said chirped grating to return to said second port, and the optical signal is made to go to said output transmission path from said third port; wherein almost all chromatic dispersion is compensated by the dispersion compensation optical fiber, and wherein the chirped grating is arranged so that only a wavelength-dependent component of the residual chromatic dispersion is compensated by the chirped grating, said chirped grating having a dispersion slope opposite to that of the residual chromatic dispersion and substantially equal in absolute value to the dispersion slope of the wavelength-dependent component of the residual chromatic dispersion.

Claim 13

A chromatic dispersion compensating optical communication system according to claim 10, wherein said optical signal directing means is an optical circulator.

Claim 14

A chromatic dispersion compensating optical communication system according to claim 10, wherein said optical signal directing means is a directional coupler.

Claim 15

A chromatic dispersion compensating optical communication system according to claim 10, wherein said chromatic dispersion compensator further comprising an optical fiber amplifier which is connected to at least one of said first and third ports.

Claim 16

A chromatic dispersion compensating optical communication system according to claim 13, wherein said dispersion compensating fiber has chromatic dispersion equal to or less than -40 ps/nm/km in said wavelength range used.

Claim 17

A chromatic dispersion compensating optical communication system according to claim 14, wherein said wavelength range used is in a range of 1540 to 1560 nm.

Claim 18

A chromatic dispersion compensating optical communication system according to claim 10, wherein said dispersion compensating fiber has chromatic dispersion equal to or less than-40 ps/nm/km in said wavelength range used.

Claim 19

A chromatic dispersion compensating optical communication system according to claim 16, wherein said wavelength range used is in a range of 1540 to 1560 nm.

Claim 20

A chromatic dispersion compensating optical communication system according to claim 10, wherein said wavelength range used is in a range of 1540 to 1560 nm.

Claim 21

A chromatic dispersion compensating optical communication system, comprising: a transmission path comprising a 1.55 μm-band single mode fiber; and a chromatic dispersion compensator which is connected to one of an intermediate and an end portion of said transmission path, said chromatic dispersion compensator comprising: optical signal directing means having first, second and third ports, for directing an optical signal input from one of said ports to another port of said ports; an input transmission path which is connected to said first port; an output transmission path which is connected to said third port; a chirped grating which is connected to said second port; and a dispersion compensating fiber which is connected to at least one of said first, second and third ports, said dispersion compensating fiber and said chirped grating having chromatic dispersion characteristics opposite to the chromatic dispersion characteristics of said input and output transmission paths, said dispersion compensating fiber having positive chromatic dispersion in a wavelength range used; wherein the optical signal is incident into said first port from said input transmission path, the optical signal is made to go out to said chirped grating from said second port, the optical signal is incident from said chirped grating to return to said second port, and the optical signal is made to go to said output transmission path from said third port; wherein almost all chromatic dispersion is compensated by the dispersion compensation optical fiber, and wherein the chirped grating is arranged so that only a wavelength-dependent component of the residual chromatic dispersion is compensated by the chirped grating, said chirped grating having a dispersion slope opposite to that of the residual chromatic dispersion and substantially equal in absolute value to the dispersion slope of the wavelength-dependent component of the residual chromatic dispersion.

Claim 22

A chromatic dispersion compensating optical communication system, comprising: a transmission path comprising a 1.55 μm-band single mode fiber; and a chromatic dispersion compensator which is connected to one of an intermediate and an end portion of said transmission path, said chromatic dispersion compensator comprising: optical signal directing means having first, second and third ports, for directing an optical signal input from one of said ports to another port of said ports; an input transmission path which is connected to said first port; an output transmission path which is connected to said third port; a chirped grating which is connected to said second port; and a dispersion compensating fiber which is connected to at least one of said first, second and third ports, said dispersion compensating fiber and said chirped grating having chromatic dispersion characteristics opposite to the chromatic dispersion characteristics of said input and output transmission paths, said dispersion compensating fiber having positive chromatic dispersion in a wavelength range used; wherein the optical signal is incident into said first port from said input transmission path, the optical signal is made to go out to said chirped grating from said second port, the optical signal is incident from said chirped grating to return to said second port, and the optical signal is made to go to said output transmission path from said third port; wherein almost all chromatic dispersion is compensated by the dispersion compensation optical fiber, and wherein the chirped grating is arranged so that only a wavelength-dependent component of the residual chromatic dispersion is compensated by the chirped grating, said chirped grating having a dispersion slope opposite to that of the residual chromatic dispersion and substantially equal in absolute value to the dispersion slope of the wavelength-dependent component of the residual chromatic dispersion.

Claim 23

A chromatic dispersion compensating optical communication system according to claim 19, wherein said optical signal directing means is an optical circulator.

Claim 24

A chromatic dispersion compensating optical communication system according to claim 19, wherein said optical signal directing means is a directional coupler.

Claim 25

A chromatic dispersion compensating optical communication system according to claim 19, wherein said chromatic dispersion compensator further comprising an optical fiber amplifier which is connected to at least one of said first and third ports.

Claim 26

A chromatic dispersion compensating optical communication system according to claim 22, wherein said wavelength range used is in a range of 1540 to 1560 nm.

Claim 27

A chromatic dispersion compensating optical communication system according to claim 19, wherein said wavelength range used is in a range of 1540 to 1560 nm.

Claim 28

A chromatic dispersion compensating optical communication system according to claim 19, wherein said dispersion compensating fiber is a 1.3 μm-band single mode fiber.

Claim 29

A chromatic dispersion compensating optical communication system according to claim 25, wherein said wavelength range used is in a range of 1540 to 1560 nm.