# US 7,613,397 B2 · Wavelength division multiplexing optical transmission system and wavelength dispersion compensation unit

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- Number: US 7,613,397 B2
- Document ID: US7613397B2
- Status: Granted
- Kind: B2
- Application number: 10/914,625
- Filed: 2004-08-10
- Published: 2005-09-29
- Granted: 2009-11-03
- Earliest claimed: 2004-03-26
- Assignees: Fujitsu Limited
- Inventors: Kentaro Nakamura; Hiroki Ooi; George Ishikawa
- Web page: https://patentgrep.com/patent/US7613397B2

## CPC

- H04B 10/2525: using dispersion-compensating fibres
- H04J 14/0213: {Groups of channels or wave bands arrangements}
- H04B: TRANSMISSION
- H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S)

## Abstract

In the WDM optical transmission system, a high-slope dispersion compensator compensates wavelength dispersion produced in the optical transmission line. The high-slope dispersion compensator has a dispersion slope characteristic, by which a dispersion slope is substantially compensated over the wavelength bandwidth of the optical transmission line, and also a dispersion compensation characteristic, by which the residual dispersion produced after compensating the dispersion slope using the above dispersion slope characteristic becomes symmetrical with respect to a wavelength in the vicinity of the center of the wavelength bandwidth. To achieve the above compensation, a wavelength-multiplexed signal is divided into wavelength bandwidth groups, and the residual dispersion of the optical transmission line is compensated on a group-by-group basis for the wavelength bandwidth groups.

## Claims

### Claim 1

A wavelength division multiplexing optical transmission system transmitting a wavelength-multiplexed signal through an optical transmission line, said wavelength division multiplexing optical transmission system comprising:
a wavelength division section comprising:
a first three-port bandpass filter dividing the wavelength-multiplexed signal into contiguous groups including a first medium bandwidth group of signals, a first shorter wavelength side end group of signals on a shorter wavelength side of the first medium bandwidth group of signals and a first longer wavelength side end group of signals on a longer wavelength side of the first medium bandwidth group of signals, and
a second three-port bandpass filter dividing the first medium bandwidth group of signals into contiguous groups including a second medium bandwidth group of signals, a second shorter wavelength side end group of signals on a shorter wavelength side of the second medium bandwidth group of signals and a second longer wavelength side end group of signals on a longer wavelength side of the second medium bandwidth of signals; and
a dispersion compensation section collectively performing dispersion compensation of at least one of
the first shorter wavelength side end group of signals and the first longer wavelength side end group of signals taken together without the first medium bandwidth group of signals, and
the second shorter wavelength side end group of signals and the second longer wavelength side end group of signals taken together without the first shorter wavelength side end group of signals, the first longer wavelengths side end group of signals and the second medium bandwidth group of signals,
to thereby compensate residual dispersion of the optical transmission line.

### Claim 2 (depends on 1)

The wavelength division multiplexing optical transmission system according to claim 1, wherein the dispersion compensation section comprises a dispersion compensator collectively performing dispersion compensation on one of:
the first shorter wavelength side end group of signals and the first longer wavelength side end group of signals taken together without the first medium bandwidth group of signals,
the second medium bandwidth group of signals taken together without the first shorter wavelength side end group of signals, the first longer wavelength side end group of signals, the second shorter wavelength side end group of signals and the second longer wavelength side end group of signals, and
the second shorter wavelength side end group of signals and the second longer wavelength side end group of signals taken together without the first shorter wavelength side end group of signals, the first longer wavelengths side end group of signals and the second medium bandwidth group of signals.

### Claim 3 (depends on 1)

The wavelength division multiplexing optical transmission system according to claim 1, wherein the dispersion compensation section comprises a VIPA (virtual imaged phased array) variable dispersion compensator collectively performing dispersion compensation on one of:
the first shorter wavelength side end group of signals and the first longer wavelength side end group of signals taken together without the first medium bandwidth group of signals,
the second medium bandwidth group of signals taken together without the first shorter wavelength side end group of signals, the first longer wavelength side end group of signals, the second shorter wavelength side end group of signals and the second longer wavelength side end group of signals, and
the second shorter wavelength side end group of signals and the second longer wavelength side end group of signals taken together without the first shorter wavelength side end group of signals, the first longer wavelengths side end group of signals and the second medium bandwidth group of signals.

### Claim 4

A wavelength dispersion compensation unit comprising:
a wavelength division section comprising:
a first three-port bandpass filter dividing a wavelength-multiplexed signal transmitted through an optical transmission line into contiguous groups including a first medium bandwidth group of signals, a first shorter wavelength side end group of signals on a shorter wavelength side of the first medium bandwidth group of signals and a first longer wavelength side end group of signals on a longer wavelength side of the first medium bandwidth group of signals, and
a second three-port bandpass filter dividing the first medium bandwidth group of signals into contiguous groups including a second medium bandwidth group of signals, a second shorter wavelength side end group of signals on a shorter wavelength side of the second medium bandwidth group of signals and a second longer wavelength side end group of signals on a longer wavelength side of the second medium bandwidth of signals; and
a dispersion compensation section collectively performing dispersion compensation of at least one of:
the first shorter wavelength side end group of signals and the first longer wavelength side end group of signals taken together without the first medium bandwidth group of signals, and
the second shorter wavelength side end group of signals and the second longer wavelength side end group of signals taken together without the first shorter wavelength side end group of signals, the first longer wavelengths side end group of signals and the second medium bandwidth group of signals,
to thereby compensate residual dispersion of the optical transmission line.

### Claim 5 (depends on 4)

The wavelength dispersion compensation unit according to claim 4, wherein the dispersion compensation section comprises a dispersion compensator collectively performing dispersion compensation on one of:
the first shorter wavelength side end group of signals and the first longer wavelength side end group of signals taken together without the first medium bandwidth group of signals,
the second medium bandwidth group of signals taken together without the first shorter wavelength side end group of signals, the first longer wavelength side end group of signals, the second shorter wavelength side end group of signals and the second longer wavelength side end group of signals, and
the second shorter wavelength side end group of signals and the second longer wavelength side end group of signals taken together without the first shorter wavelength side end group of signals, the first longer wavelengths side end group of signals and the second medium bandwidth group of signals.

### Claim 6 (depends on 4)

The wavelength dispersion compensation unit according to claim 4, wherein the dispersion compensation section comprises a VIPA (virtual imaged phased array) variable dispersion compensator collectively performing dispersion compensation on one of:
the first shorter wavelength side end group of signals and the first longer wavelength side end group of signals taken together without the first medium bandwidth group of signals,
the second medium bandwidth group of signals taken together without the first shorter wavelength side end group of signals, the first longer wavelength side end group of signals, the second shorter wavelength side end group of signals and the second longer wavelength side end group of signals, and
the second shorter wavelength side end group of signals and the second longer wavelength side end group of signals taken together without the first shorter wavelength side end group of signals, the first longer wavelengths side end group of signals and the second medium bandwidth group of signals.

### Claim 7

An apparatus comprising:
a first three-port bandpass filter dividing a wavelength-multiplexed signal transmitted through an optical transmission line into contiguous groups including a first medium bandwidth group of signals, a first shorter wavelength side end group of signals on a shorter wavelength side of the first medium bandwidth group of signals and a first longer wavelength side end group of signals on a longer wavelength side of the first medium bandwidth group of signals;
a second three-port bandpass filter dividing the first medium bandwidth group of signals into contiguous groups including a second medium bandwidth group of signals, a second shorter wavelength side end group of signals on a shorter wavelength side of the second medium bandwidth group of signals and a second longer wavelength side end group of signals on a longer wavelength side of the second medium bandwidth of signals; and
a dispersion compensation section collectively performing dispersion compensation of at least one of:
the first shorter wavelength side end group of signals and the first longer wavelength side end group of signals taken together without the first medium bandwidth group of signals, and
the second shorter wavelength side end group of signals and the second longer wavelength side end group of signals taken together without the first shorter wavelength side end group of signals, the first longer wavelengths side end group of signals and the second medium bandwidth group of signals.

### Claim 8 (depends on 7)

An apparatus as in claim 7, wherein, to collectively perform dispersion compensation, the dispersion compensation section comprises:
a virtual imaged phased array (VIPA) variable dispersion compensator.

### Claim 9 (depends on 7)

An apparatus as in claim 7, wherein the dispersion compensation section comprises:
a first dispersion compensator collectively compensating dispersion of the second medium bandwidth group of signals taken together without the first shorter wavelength side end group of signals, the first longer wavelength side end group of signals, the second shorter wavelength side end group of signals and the second longer wavelength side end group of signals, and
a second dispersion compensator collectively compensating dispersion of the second shorter wavelength side end group of signals and the second longer wavelength side end group of signals taken together without the first shorter wavelength side end group of signals, the first longer wavelengths side end group of signals and the second medium bandwidth group of signals,
wherein each of the first and second dispersion compensators is:
a virtual imaged phased array (VIPA) variable dispersion compensator.

### Claim 10

An apparatus comprising:
a first three-port bandpass filter dividing a wavelength-multiplexed signal transmitted through an optical transmission line into contiguous groups including a first medium bandwidth group of signals, a first shorter wavelength side end group of signals on a shorter wavelength side of the first medium bandwidth group of signals and a first longer wavelength side end group of signals on a longer wavelength side of the first medium bandwidth group of signals,
a second three-port bandpass filter dividing the first medium bandwidth group of signals into contiguous groups including a second medium bandwidth group of signals, a second shorter wavelength side end group of signals on a shorter wavelength side of the second medium bandwidth group of signals and a second longer wavelength side end group of signals on a longer wavelength side of the second medium bandwidth of signals; and
means for collectively performing dispersion compensation of at least one of:
the first shorter wavelength side end group of signals and the first longer wavelength side end group of signals taken together without the first medium bandwidth group of signals, and
the second shorter wavelength side end group of signals and the second longer wavelength side end group of signals taken together without the first shorter wavelength side end group of signals, the first longer wavelengths side end group of signals and the second medium bandwidth group of signals.