JP3408378B2 - Optical repeater amplifier - Google Patents

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical amplifying device used for wavelength division multiplexed optical transmission and an optical repeater amplifying device using the same, and more particularly to an optical amplifying device for reducing a level difference between wavelengths.

[0001]

2. Description of the Related Art A conventional optical wavelength division multiplexed signal transmission system, as shown in FIG. 2, includes a light source 1 of LD λ1 to LD λn,
It comprises a star coupler 2 that performs optical wavelength multiplexing, and an optical direct amplifier 3 that collectively amplifies optical wavelength multiplexed signals (λ1 to λn) in multiple channels.

A light source 1 of LD λ1 to LD λn is wavelength-multiplexed with a star coupler 2 to generate an optical wavelength multiplexed signal (λ1 to λ
n) is input to the optical direct amplifier 3, and the optical wavelength division multiplexed signal is amplified in a multi-channel manner and sent to the transmission line.

Long-distance transmission is performed while compensating for the loss in the transmission line by connecting optical direct amplifiers in multiple stages.

[0004]

When multi-channel batch amplification is performed in a fiber type optical direct amplifier during transmission of an optical wavelength multiplexed signal, a deviation occurs in the level of each channel due to the gain wavelength dependence of the optical direct amplifier. Furthermore, when optical direct amplifiers are connected in multiple stages and relay transmission is performed, there is a problem that the level deviation becomes large and the optical receiving sensitivity on the receiving side varies and the system becomes unstable.

[0005]

In order to eliminate the above-mentioned drawbacks, a plurality of optical signals of different wavelengths are input and the optical amplifier and the optical repeater amplifier of the present invention optically amplify these optical signals. And output an amplified optical signal, an amplified optical signal brancher that branches a part of the amplified optical signal and outputs a branched amplified optical signal, and extracts the shortest wavelength light from the branched amplified optical signal And a level detection circuit for detecting the level of the shortest wavelength channel and the level of the longest wavelength channel by extracting light of the longest wavelength of the wavelengths from the branched amplified optical signal, and the channel level of the shortest wavelength and the channel of the longest wavelength. A difference detection circuit that detects a level difference and sends a control signal according to the difference; and an amplified optical signal control circuit that receives the control signal and controls the output of the amplified optical signal of each wavelength so as to reduce the difference. Equipped with It is characterized in Rukoto.

Here, the amplification optical signal control circuit is arranged between the optical amplifier and the amplification optical signal branching device, and is characterized in that it gives a loss determined to each optical signal according to the wavelength of the optical signal. . The amplified optical signal control circuit is characterized by being a Mach-Zehnder waveguide type optical filter arranged between the optical amplifier and the amplified optical signal branching device.

Further, the level detection circuit includes an optical branching device for branching the branched amplified optical signal into two and outputting a first branched light and a second branched light, and a shortest wavelength of the above wavelengths from the first branched light. Output only the shortest wavelength light by selectively transmitting only the first light
Optical filter for outputting the longest wavelength light by selectively transmitting only the longest wavelength light of the above wavelengths from the second branched light, and the shortest wavelength light and the longest wavelength light. And a photoelectric converter for converting the signal.

The optical repeater / amplifier of the present invention is characterized in that the optical repeater station includes the optical amplifying device having the above configuration.

More specifically, the optical amplifying device of the present invention is
MZ with built-in thin film resistance electrode for inputting output of optical amplifier
Waveguide type optical filter, coupler for optically branching output of MZ waveguide type optical filter, optical coupler for branching one of the couplers into two and inputting to optical BPF, optical BPF for extracting shortest wavelength channel, and longest wavelength Optical BPF for extracting channel
And an optical / electrical conversion circuit for detecting the level of the shortest wavelength channel by performing optical / electrical conversion on the output of the optical BPF, an optical / electrical conversion circuit for detecting the level of the longest wavelength channel, the level of the shortest wavelength channel and the longest wavelength It is composed of a difference detection circuit for detecting the difference in channel level and an electrode control circuit for controlling the electrodes of the MZ waveguide type optical filter so that the difference becomes "0".

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical amplifying device of the present invention and an optical repeater amplifying device using the same will be described with reference to the drawings. FIG. 1 shows an embodiment of the present invention.

A light source 1 of LD λ1 to LD λn is wavelength-multiplexed by a star coupler 2. Optical wavelength multiplexed signal (λ1 to λ
n) is input to the optical direct amplifier 3 to amplify the optical wavelength division multiplexed signal in multiple channels at once. At this time, a deviation occurs in the output level of each channel due to the gain wavelength dependence of the optical direct amplifier 3.
Generally, the gain wavelength dependence of the optical direct amplifier is gradual, and it is known that either the channel level on the longest wavelength side or the channel level on the shortest wavelength side becomes the lowest.

The output of the optical direct amplifier 2 is input to the MZ waveguide type optical filter 5. The MZ waveguide type optical filter 5 is provided with a thin film resistance electrode, and a voltage is applied to the electrode so that the filter characteristics can be changed. MZ waveguide type optical filter 5
The output of 1 is branched by the optical coupler 6 and one is sent to the transmission line.
The other side is branched into two by an optical coupler 7, and an optical BPF 8 and
Input to the optical BPF 9, and the optical BPF 8 has λ1 (shortest wavelength channel) and the optical BPF 9 has λn (longest wavelength channel).
Pull out. The extracted λ1 and λn are input to the optical / electrical conversion circuit 10 and the optical / electrical conversion circuit 11, respectively, and the levels of λ1 (shortest wavelength channel) and λn (longest wavelength channel) are detected.

Since either λ1 or λn is the lowest among all channels, the difference detection circuit 12 detects the difference.
Then, the electrode of the MZ waveguide type optical filter is controlled using the electrode control circuit 13 so that the difference becomes “0”, and the gain equalization of the optical direct amplifier 2 is performed by adjusting the inclination of the optical filter characteristic.

[0014]

As described above, since the automatic gain equalization of the optical direct amplifier is performed by using the waveguide type optical filter, even if the optical direct amplifier is used for the multi-stage relay of the optical wavelength division multiplexed signal, The level deviation does not occur, variations in optical reception sensitivity between channels are suppressed, and a stable optical wavelength multiplexing system can be constructed.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of an optical amplifying device of the present invention and an optical repeater amplifying device using the same.

FIG. 2 is a diagram showing a configuration of an example of an optical repeater amplifier including a conventional optical amplifier in a repeater station.

[Explanation of symbols]

1 Laser diode (LD) λ1 to λn light source 2 Optical multiplexer 3 Optical amplifier 4 Automatic gain equivalent circuit 5 Mach-Zehnder Waveguide Optical Filter 6 Optical splitter 7 Optical splitter 8 optical bandpass filters 9 Optical bandpass filter 10 photoelectric conversion circuit 11 Photoelectric conversion circuit 12 Difference detection circuit 13-electrode control circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-147114 (JP, A) JP-A-7-30520 (JP, A) Yasushi Sugaya, Susumu Kinoshita, Terumi Konma "Wavelength Multiplexed Er-doped Fiber Optics" Examination of amplifier configuration method ", IEICE Technical Report, The Institute of Electronics, Information and Communication Engineers, July 1995, OCS95-36, p. 21-26 (58) Fields surveyed (Int.Cl. ⁷ , DB name) H04B 10/00-10/28 H04J 14/00

Claims (3)

(57) [Claims] 1. Optical amplification means for inputting optical signals having a plurality of different wavelengths, optically amplifying the optical signals in multiple channels and outputting an amplified optical signal, and branching a part of the amplified optical signal. Amplified optical signal branching means for outputting a branched amplified optical signal, a level of the shortest wavelength channel by extracting light of the shortest wavelength among the wavelengths from the branched amplified optical signal, and the wavelength from the branched amplified optical signal Level detection means for extracting the light of the longest wavelength among them to detect the level of the longest wavelength channel, and a control signal according to the difference for detecting the difference between the channel level of the shortest wavelength and the channel level of the longest wavelength Which is arranged between the optical amplifying means and the amplified optical signal branching means and which receives the control signal and gives the optical signal a loss determined according to the wavelength of the optical signal. Before Optical repeater amplifier device comprising an amplifying optical signal control means for controlling the output of the amplifying optical signals of each wavelength so as to reduce the difference. 2. The optical repeater according to claim 1, wherein the amplified optical signal control means is a Mach-Zehnder waveguide type optical filter arranged between the optical amplification means and the amplified optical signal branching means. Amplification device . 3. The level detecting means, an optical branching device for branching the branched amplified optical signal into two to output a first branched light and a second branched light, and a level of the wavelength from the first branched light. A first optical filter that selectively transmits only the light of the shortest wavelength and outputs light of the shortest wavelength; and a longest that selectively transmits only the light of the longest wavelength of the wavelengths from the second branched light. A second optical filter that outputs wavelength light, a first opto-electric converter that converts the shortest wavelength light into an electrical signal, and a second opto-electric converter that converts the longest wavelength light into an electrical signal. The optical repeater amplifier according to claim 1 or 2, wherein the optical repeater amplifier is included .