US 6,587,242 B1Granted

Optical transmission system

AssigneeNippon Telegraph and Telephone Corporation

InventorsIppei Shake, Hidehiko Takara, Yoshiaki Yamabayashi, Osamu Kamatani, Koji Nonaka, Kentaro Uchiyama

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Abstract

It is the object of the present invention to provide a transmission system that transmits a control signal corresponding to the overhead accommodating time division multiplexing information at a frequency that is the same (or nearly the same) as that of the main signal. In order to attain this object, an optical transmitter broadens in a time range the optical waveform of the OTDM signal having a wavelength λ0 and the control light having a wavelength λ1(≈λ0), and multiplexes the signal light having an optical peak intensity set low compared to the OTDM signal peak intensity and sending this to an optical transmission fiber. An optical receiver provides a light splitting means that splits into two parts the transmitted OTDM signal and the control light and outputs one part thereof to an optical time division multiplexing means, and at the same time restores the control light included in the other part of the light to the original optical pulse train, and extracts the control information by converting this to an electric signal.

Claims29

Dependent claims

An optical transmission system that transmits to an optical receiver a signal light sent from an optical transmitter via a plurality of optical transmission fibers connected in serial and an optical linear repeater or an optical regenerator repeater, comprising:

an optical transmitter including:
an optical time division multiplexed signal generating means that outputs an optical time division multiplexed OTDM signal having a wavelength λ0 that has a time division multiplexed signal light having N lines (N is an integer equal to or greater than 2) and having a bit rate mif0(i=1, 2, . . . , N, where m1 is an integer equal to or greater than 1) that is an integral multiple of a fundamental frequency f0;
a control light generation means that generates control signal light wherein an optical pulse train, having a wavelength λ1 equal or almost equal to the wavelength of the OTDM signal and having a bit rate kf0 that is an integral multiple of the fundamental frequency f0 that are synchronized with the OTDM signal, is modulated by control information of said OTDM signal;
an optical pulse broadening means that broadens the optical pulse waveform of the control signal in a time range, and outputs a control light having an optical peak intensity set sufficiently low in comparison to the OTDM signal peak intensity;
and
an optical coupling means that multiplexes the OTDM signal and the control light and delivers them to the optical transmission fiber;
and
an optical receiver including:
a light splitting means that splits into two parts the transmitted light;
an optical pulse narrowing means that restores the control light that includes a part of the light split by the optical splitting means to the original optical pulse train;
an optoelectric conversion means that converts the output light of the optical pulse narrowing means to an electric signal;
a control signal processing means that extracts from the electrical signal information relating to the optical time division multiplexing of the OTDM signal and control information including a timing clock;
and
an optical time division demultiplexing means that, depending on the control information, carries out optical time division demultiplexing of the OTDM signal into an N line signal light included in the other portion of light split by the optical splitting means.

11 more elements

An optical transmission system that transmits to an optical receiving means a signal light sent from an optical transmitter via a plurality of optical transmission fibers connected in serial and an optical linear repeater, comprising:

a signal generation means that generates signal light having a wavelength λ0 and a bit rate f0;
a monitor light generating means that generates monitor light of an optical pulse train having a wavelength λ1 equal to or almost equal to the wavelength of the signal light and having a repetition rate f1;
an optical pulse broadening means that outputs monitor light having an optical peak intensity set sufficiently low compared to the signal light peak intensity;
and
an optical coupling means that multiplexes signal light and monitor light output from the optical pulse broadening means and delivers the monitor light to the optical transmission fiber;
and
an optical receiver including:
a wavelength dispersion adjustment means that provides wavelength dispersion to the delivered light;
an optical splitting means that splits into two parts the output light of the wavelength dispersion adjustment means and outputs one part to a signal light processing means that carries out reception processing of the signal light;
an optical pulse narrowing means that restores the monitor light included in the other part of the light split by the optical splitting means to the original pulse train;
an optoelectric conversion means that converts the output light of the optical pulse narrowing means into an electric signal;
a monitor clock detection means that detects a clock component of the monitor light from the electric signal;
and
a wavelength dispersion compensation amount control means that controls the wavelength dispersion compensation amount of the wavelength dispersion adjustment means so that the clock component is maximized.

11 more elements

Dependencies are inferred from the claim text.