Wavelength control method and optical communication apparatus for performing wavelength division multiplex communication

Claim 2

An output light wavelength control method for an optical transmitter used in an optical communication system for performing wavelength division multiplex communication on an optical transmission path, said method comprising the steps of: detecting a wavelength of light on the optical transmission path; searching for an unoccupied space, in which light to be output from said optical transmitter does not interfere with another light on the optical transmission path, based on a result of said detecting step; controlling the wavelength of the light to be output from said optical transmitter so that the light to be output has a wavelength within the unoccupied space; setting, as a reference side wavelength, a wavelength of another light which is adjacent to the wavelength of the light to be output from said optical transmitter on one of the longer and shorter wavelength sides along a wavelength axis; and controlling an interval between the wavelength of the light to be output and the reference side wavelength to assure that the interval is close to a predetermined first wavelength interval.

Claim 3

A method according to claim 1, said detecting step detecting the wavelength by sweeping a detectable wavelength of wavelength detection means in the transmitter.

Claim 4

A method according to claim 2, said detecting step detecting the wavelength by sweep-detecting a region including at least a wavelength variable range of the output light from said optical transmitter.

Claim 5

A method according to claim 2, wherein, in said detecting step, light-emission means of said optical transmitter is controlled to emit light upon sweep detection, light output from the light-emission means is input to the wavelength detection means, and the detectable wavelength of the wavelength detection means is swept to detect a wavelength of the light output from the light-emission means of said optical transmitter together with a wavelength of another light on the optical transmission path.

Claim 6

A method according to claim 4, wherein light output from the light-emission means of said optical transmitter is input to the wavelength detection means without being output onto the optical transmission path to detect a wavelength of the light output from the light-emission means of said optical transmitter together with a wavelength of another light on the optical transmission path.

Claim 7

A method according to claim 4, wherein, in said detecting step, the wavelength of the light output from the light-emission means of said optical transmitter is distinguished from the wavelength of the other light on the optical transmission path by comparing a sweep detection result obtained when the light-emission means of said optical transmitter emits light with a sweep detection result obtained when the light-emission means of said optical transmitter does not emit light.

Claim 8

A method according to claim 1, wherein, in said step of controlling the wavelength of the light to be output, a detectable wavelength of wavelength detection means of said optical transmitter is set within the unoccupied space identified in said searching step, and a wavelength of light output from light-emission means of said optical transmitter is swept to match the detectable wavelength, so as to control the light-emission means to emit light at a wavelength in the unoccupied space.

Claim 9

A method according to claim 7, wherein, in said setting step, the detectable wavelength is set at an end portion on one of the longer and shorter wavelength sides in the unoccupied space.

Claim 10

A method according to claim 1, wherein light output from light-emission means of said optical transmitter is not output onto the optical transmission path before the light-emission means of said optical transmitter is controlled in said step of controlling the wavelength of the light to be output to emit light at a wavelength within the unoccupied space.

Claim 11

A method according to claim 1, wherein, in said step of controlling the wavelength interval, the wavelength interval between the light to be output from said optical transmitter and the reference side wavelength is always detected, and light-emission means of said optical transmitter is controlled to assure that the wavelength interval is close to the first wavelength interval.

Claim 12

A method according to claim 1, further comprising a step of detecting the number of wavelengths belonging to each of a plurality of wavelength groups each consisting of a plurality of wavelengths, each of the plurality of wavelengths being assigned on the optical transmission path at predetermined wavelength intervals, and wherein a wavelength at an end portion of the wavelength group which falls within the wavelength variable range of the output light of said optical transmitter and includes a largest number of wavelengths is set to be the reference side wavelength.

Claim 13

A method according to claim 11, wherein, in said step of searching for the unoccupied space, the number of wavelengths is detected.

Claim 14

A method according to claim 1, wherein when the wavelength interval between the reference side wavelength and the wavelength of the light to be output from said optical transmitter is controlled in said step of controlling the wavelength interval to have a value near the predetermined first wavelength interval, and when a wavelength interval between the wavelength of the light to be output from said optical transmitter and an opposite side wavelength adjacent to the wavelength of the light to be output from said optical transmitter on a side opposite to the reference side wavelength becomes not more than a predetermined second interval, the opposite side wavelength is set to be the reference side wavelength.

Claim 15

An output light wavelength control method for an optical transmitter used in an optical communication system for performing wavelength division multiplex communication on an optical transmission path, said method comprising the steps of: detecting a wavelength of light on the optical transmission path; setting, as a reference side wavelength, a wavelength of another light which is adjacent to the wavelength of the light to be output from said optical transmitter on one of the longer and shorter wavelength sides along a wavelength axis; controlling an interval between the wavelength of the light to be output and the reference side wavelength to assure that the interval is close to a predetermined first wavelength interval; and controlling to set an opposite side wavelength, which is adjacent to the wavelength of the light to be output from said optical transmitter on a side opposite to the reference side wavelength, to be the reference side wavelength, when the wavelength interval between the reference side wavelength and the wavelength of the light to be output from said optical transmitter is maintained to have a value near the predetermined first wavelength interval, and when a wavelength interval between the wavelength of the light to be output from said optical transmitter and the opposite side wavelength becomes not more than a predetermined second interval.

Claim 16

An output light wavelength control method for an optical transmitter used in an optical communication system for performing wavelength division multiplex communication on an optical transmission path, said method comprising the steps of: detecting a wavelength of light on the optical transmission path; setting, as a reference side wavelength, a wavelength of another light which is adjacent to the wavelength of the light to be output from said optical transmitter on one of the longer and shorter wavelength sides along a wavelength axis; controlling an interval between the wavelength of the light to be output and the reference side wavelength to assure that the interval is close to a predetermined first wavelength interval; and controlling to set an opposite side wavelength, which is adjacent to the wavelength of the light to be output from said optical transmitter on a side opposite to the reference side wavelength, to be the reference side wavelength, when the wavelength interval between the reference side wavelength and the wavelength of the light to be output from said optical transmitter is maintained to have a value near the predetermined first wavelength interval, and when a wavelength interval between the wavelength of the light to be output from said optical transmitter and the opposite side wavelength becomes not more than a predetermined second interval.

Claim 17

A method according to claim 14, said detecting step detecting the wavelength by sweeping a detectable wavelength of wavelength detection means in the transmitter.

Claim 18

A method according to claim 15, said detecting step detecting the wavelength by sweep-detecting a region including at least a wavelength variable range of the output light from said optical transmitter.

Claim 19

A method according to claim 15, wherein, in said detecting step, light-emission means of said optical transmitter is controlled to emit light upon sweep detection, light output from the light-emission means is input to the wavelength detection means, and the detectable wavelength of the wavelength detection means is swept to detect a wavelength of the light output from the light-emission means of said optical transmitter together with a wavelength of another light on the optical transmission path.

Claim 20

A method according to claim 17, wherein light output from the light-emission means of said optical transmitter is input to the wavelength detection means without being output onto the optical transmission path to detect a wavelength of the light output from the light-emission means of said optical transmitter together with a wavelength of another light on the optical transmission path.

Claim 21

A method according to claim 17, in said detecting step, the wavelength of the light output from the light-emission means of said optical transmitter is distinguished from the wavelength of the other light on the optical transmission path by comparing a sweep detection result obtained when the light-emission means of said optical transmitter emits light with a sweep detection result obtained when the light-emission means of said optical transmitter does not emit light.

Claim 22

A method according to claim 14, wherein before said step of controlling an interval between the reference side wavelength and the wavelength of the light to be output from said optical transmitter, said method further comprises the steps of: searching for an unoccupied space, in which light to be output from said optical transmitter does not interfere with another light on the optical transmission path, based on a result of said detecting step; and controlling the wavelength of the light to be output from said optical transmitter so that the light to be output has a wavelength within the unoccupied space.

Claim 23

A method according to claim 20, wherein, in said step of controlling the wavelength of the out-put light to be output, a detectable wavelength of wavelength detection means of said optical transmitter is set within the unoccupied space identified in said searching step, and a wavelength of light output from light-emission means of said optical transmitter is swept to match the detectable wavelength, so as to control the light-emission means to emit light at a wavelength in the unoccupied space.

Claim 24

A method according to claim 21, wherein, in said setting step, the detectable wavelength is set at an end portion on one of the longer and shorter wavelength sides in the unoccupied space.

Claim 25

A method according to claim 20, wherein light output from light-emission means of said optical transmitter is not output onto the optical transmission path until the light-emission means of said optical transmitter is controlled in said step of controlling the wavelength of the light to be output from said optical transmitter to emit light at a wavelength within the unoccupied space.

Claim 26

A method according to claim 14, wherein, in said step of controlling the wavelength interval, the wavelength interval between the light to be output from said optical transmitter and the reference side wavelength is always detected, and light-emission means of said optical transmitter is controlled to assure that the wavelength interval is close to the first wavelength interval.

Claim 27

A method according to claim 14, further comprising a step of detecting the number of wavelengths belonging to each of a plurality of wavelength groups each consisting of a plurality of wavelengths, each of the plurality of wavelengths being assigned on the optical transmission path at predetermined wavelength intervals, and wherein a wavelength at an end portion of the wavelength group which falls within the wavelength variable range of the light to be output of said optical transmitter and includes a largest number of wavelengths is set to be the reference side wavelength.

Claim 28

A method according to claim 25, wherein in said step of searching for the unoccupied space, the number of wavelengths is detected.

Claim 29

An optical transmitter used in an optical communication system for performing a wavelength division multiplex communication on an optical transmission path, said transmitter comprising: light-emission means for outputting light; wavelength detection means for detecting a wavelength of light on the optical transmission path and for detecting a wavelength of the output light from said light-emission means; means for recognizing an unoccupied space, in which the light to be output from said optical transmitter does not interfere with another light on the optical transmission path, based on a detection result of the wavelength of the light on the optical transmission path by said wavelength detection means; setting means for setting, as a reference side wavelength, a wavelength of another light which is adjacent to the wavelength of the light to be output from said optical transmitter on one of the longer and shorter wavelength sides along a wavelength axis; and control means for performing wavelength control to control a wavelength interval between the reference side wavelength and the wavelength of the light to be output from said optical transmitter to assure that the interval is close to a predetermined first wavelength interval.

Claim 30

An optical transmitter used in an optical communication system for performing a wavelength division multiplex communication on an optical transmission path, said transmitter comprising: light-emission means for outputting light; wavelength detection means for detecting a wavelength of light on the optical transmission path and for detecting a wavelength of the output light from said light-emission means; means for recognizing an unoccupied space, in which the light to be output from said optical transmitter does not interfere with another light on the optical transmission path, based on a detection result of the wavelength of the light on the optical transmission path by said wavelength detection means; setting means for setting, as a reference side wavelength, a wavelength of another light which is adjacent to the wavelength of the light to be output from said optical transmitter on one of the longer and shorter wavelength sides along a wavelength axis; and control means for performing wavelength control to control a wavelength interval between the reference side wavelength and the wavelength of the light to be output from said optical transmitter to assure that the interval is close to a predetermined first wavelength interval.

Claim 31

An optical transmitter according to claim 27, further comprising means for recognizing the number of wavelengths belonging to each of a plurality of wavelength groups each consisting of a plurality of wavelengths each of the plurality of wavelengths being assigned on the optical transmission path at predetermined wavelength intervals.

Claim 32

An optical transmitter according to claim 28, wherein said means for recognizing the unoccupied space also serves as said means for recognizing the number of wavelengths belonging to each of a plurality of wavelength groups.

Claim 33

An optical transmitter according to claim 27, said wavelength detection means comprising a wavelength variable bandpass filter for controlling a wavelength.

Claim 34

An optical transmitter according to claim 27, said light-emission means comprising a wavelength variable laser for controlling a wavelength.

Claim 35

An optical transmitter/receiver used in an optical communication system for performing a wavelength division multiplex communication on an optical transmission path, said optical transmitter/receiver comprising: an optical transmitter comprising: light-emission means for outputting light; wavelength detection means for detecting a wavelength of light on the optical transmission path and for detecting a wavelength of the output light from said light-emission means; means for recognizing an unoccupied space, in which the output light to be output from said optical transmitter does not interfere with another light on the optical transmission path, based on a detection result of the wavelength of the light on the optical transmission path by said wavelength detection means; setting means for setting, as a reference side wavelength, a wavelength of another light which is adjacent to the wavelength of the light to be output from said optical transmitter on one of the longer and shorter wavelength sides along a wavelength axis; control means for performing wavelength control to control a wavelength interval between the reference side wavelength and the wavelength of the light to be output from said optical transmitter to assure that the interval is close to a predetermined first wavelength interval; and a receiver for selecting an optical signal to be received by said optical transmitter/receiver from input optical signals, and receiving the optical signal so as to change a reception wavelength to follow a variation in wavelength of the optical signal.

Claim 36

An optical transmitter/receiver used in an optical communication system for performing a wavelength division multiplex communication on an optical transmission path, said optical transmitter/receiver comprising: an optical transmitter comprising: light-emission means for outputting light; wavelength detection means for detecting a wavelength of light on the optical transmission path and for detecting a wavelength of the output light from said light-emission means; means for recognizing an unoccupied space, in which the output light to be output from said optical transmitter does not interfere with another light on the optical transmission path, based on a detection result of the wavelength of the light on the optical transmission path by said wavelength detection means; setting means for setting, as a reference side wavelength, a wavelength of another light which is adjacent to the wavelength of the light to be output from said optical transmitter on one of the longer and shorter wavelength sides along a wavelength axis; control means for performing wavelength control to control a wavelength interval between the reference side wavelength and the wavelength of the light to be output from said optical transmitter to assure that the interval is close to a predetermined first wavelength interval; and a receiver for selecting an optical signal to be received by said optical transmitter/receiver from input optical signals, and receiving the optical signal so as to change a reception wavelength to follow a variation in wavelength of the optical signal.

Claim 37

An optical communication system for performing a wavelength division multiplex communication by connecting a plurality of terminal stations each having an optical transmitter, each optical transmitter comprising: light-emission means for outputting light; wavelength detection means for detecting a wavelength of light on the optical transmission path and for detecting a wavelength of the output light from said light-emission means; means for recognizing an unoccupied space, in which the light to be output from said optical transmitter does not interfere with another light on the optical transmission path, based on a detection result of the wavelength of the light on the optical transmission path by said wavelength detection means; and setting means for setting, as a reference side wavelength, a wavelength of another light which is adjacent to the wavelength of the light to be output from said optical transmitter on one of the longer and shorter wavelength sides along a wavelength axis, wherein, in said optical communication system, transmission wavelengths of said optical transmitters of said plurality of terminal stations are wavelength-multiplexed in turn from one of the longer and shorter wavelength sides on a wavelength axis in an unoccupied space within a wavelength range, in which said optical transmitter of each of said plurality of terminal stations that perform transmission can emit light, in a transmission start order.

Claim 38

An optical communication system for performing a wavelength division multiplex communication by connecting a plurality of terminal stations each having an optical transmitter, each optical transmitter comprising: light-emission means for outputting light; wavelength detection means for detecting a wavelength of light on the optical transmission path and for detecting a wavelength of the output light from said light-emission means; means for recognizing an unoccupied space, in which the light to be output from said optical transmitter does not interfere with another light on the optical transmission path, based on a detection result of the wavelength of the light on the optical transmission path by said wavelength detection means; and setting means for setting, as a reference side wavelength, a wavelength of another light which is adjacent to the wavelength of the light to be output from said optical transmitter on one of the longer and shorter wavelength sides along a wavelength axis, wherein, in said optical communication system, transmission wavelengths of said optical transmitters of said plurality of terminal stations are wavelength-multiplexed in turn from one of the longer and shorter wavelength sides on a wavelength axis in an unoccupied space within a wavelength range, in which said optical transmitter of each of said plurality of terminal stations that perform transmission can emit light, in a transmission start order.

Claim 39

A method according to claim 1, wherein in said detecting step the wavelength of light is detected by a wavelength filter.

Claim 40

A method according to claim 14, wherein in said detecting step the wavelength of light is detected by a wavelength filter.