# US 6,724,955 B2 · Add-drop multiplexer with signal amplification ability

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- Number: US 6,724,955 B2
- Document ID: US6724955B2
- Status: Granted
- Kind: B2
- Application number: 09/854,758
- Filed: 2001-05-14
- Published: 2003-02-20
- Granted: 2004-04-20
- Earliest claimed: 2000-05-16
- Assignees: Yutaka Sasaki; Toyokuni Electric Cable Co., Ltd.
- Inventors: Yutaka Sasaki; Hirohisa Yokota; Yoshitaka Satoda
- Web page: https://patentgrep.com/patent/US6724955B2

## CPC

- G02B 6/29383: {Adding and dropping}
- G02B 6/29334: {Grating-assisted evanescent light guide couplers, i.e. comprising grating at or functionally associated with the coupling region between the light guides, e.g. with a grating positioned where light fields overlap in the coupler}
- G02B 6/29355: {Cascade arrangement of interferometers}
- H04J 14/0201: {Add-and-drop multiplexing}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- 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

Grating built-in type optical fiber couplers and optical amplifiers form a multiplexer for efficiently effecting multiplex separation of a specific wavelength without using an optical circulator. A function to add a signal of specific wavelength efficiently can be realized. Additionally, the device is inexpensive.

## Claims

### Claim 1

An add-drop multiplexer with signal amplification ability comprising:
a first optical coupler, of a grating built-in type, having an input port, a through port, a forward coupled port, and a reverse coupled port;
a first optical amplifier having an input port for receiving a signal and an output port connected to the input port of the first optical coupler;
a second optical coupler, of a grating built-in type, having an input port, a through port not connected to the through port of the first optical coupler, a forward coupled port connected to the forward coupled port of the first optical coupler, and a reverse coupled port connected to the reverse coupled port of the first optical coupler; and
a second optical amplifier having an output, and an input connected to the input port of the second optical coupler wherein a Bragg wavelength, output by the reverse coupled port of the first optical coupler and input to the reverse coupled port of the second optical coupler, is outputted by the input port of the second optical coupler and amplified and outputted by the second optical amplifier.

### Claim 2 (depends on 1)

The add-drop multiplexer of claim 1, wherein the first and second optical couplers each include a fiber coupler formed with a fiber grating at a melt-extended portion of the fiber coupler, a pitch of the fiber grating has an uniform structure in a length direction, apodization is done, and the fiber grating has a length of 2.0 mm and a change in induced refractive index is 0.001.

### Claim 3 (depends on 2)

The add-drop multiplexer of claim 2, further comprising a switch connecting the reverse coupled port of the second optical coupler to the reverse coupled port of the first optical coupler.

### Claim 4 (depends on 3)

The add-drop multiplexer of claim 3, wherein the first and second optical couplers have a same Bragg wavelength.

### Claim 5 (depends on 2)

The add-drop multiplexer of claim 2, wherein the first and second optical couplers have a same Bragg wavelength.

### Claim 6 (depends on 1)

The add-drop multiplexer of claim 1, further comprising a switch connecting the reverse coupled port of the second optical coupler to the reverse coupled port of the first optical coupler.

### Claim 7 (depends on 6)

The add-drop multiplexer of claim 6, wherein the first and second optical couplers have a same Bragg wavelength.

### Claim 8 (depends on 1)

The add-drop multiplexer of claim 1, wherein the first and second optical couplers have a same Bragg wavelength.