JP2000232413A - Optical subscriber system, and two-way optical transmission system using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a two-way optical transmission system capable of reducing the number of used optical parts and economizing an ONU (optical subscriber line terminal unit). SOLUTION: When an outgoing light signal (λ1) from a center station 6 is inputted to a semiconductor external modulator 21 in the ONU 2 for λ1 in a subscriber house 1, the reception of the outgoing light signal (λ1) can be received if a bias is previously given from a bias circuit 22 to the semiconductor external modulator 21. Laser beams for λ1 in the center station 6 are continuously emitted and only laser beams of λ1 in the center station 6 is reflected on a grating fiber 200. When a transmission signal 111 to which the bias is given is inputted to a bias circuit 22, the semiconductor external modulator 21 modulates the outer intensity of light of λ1 from the center station 6 and reflected light in the grating fiber 200 and outputs them. The light signal of the waveform of λ2, which passes through the semiconductor external modulator 21 and the grating fiber 9, is received by ONU 3 for λ2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical subscriber system and a bidirectional optical transmission system using the same, and more particularly to an optical subscriber system.
The present invention relates to an optical subscriber system using U (Optical Network Unit).

[0002]

2. Description of the Related Art Conventionally, in this type of optical subscriber system, as shown in FIG.
9 and a subscriber's house 8 having an ONU 10 for λ2 are connected via an optical fiber transmission line 100.

[0003] The ONU 9 for λ1 is a WDM (Wavelen).
gth Division Multiplex) 91
, An optical waveguide type optical coupler 92, a PIN photodiode 83, and a laser diode 94. The ONU 10 for λ2 includes a light receiving element 11 and a gate 12.

The downstream optical signal (λ1) 10 from the center station 1
1 and the downstream optical signal (λ2) 102 are separated by the WDM 91 of the ONU 9 for λ1 in the subscriber's house 8, and the downstream optical signal (λ1) 101 is separated from the optical waveguide type optical coupler 92 of the ONU 9 for λ1. To the downstream optical signal (λ
2) 102 is input to the light receiving element 11 of the ONU 10 for λ2.

The ONU 9 for λ1 converts the downstream optical signal (λ1) 101 separated by the WDM 91 into an optical waveguide type optical coupler 92.
Input to the PIN photodiode 93, and optically receives it as a reception signal # 1.

On the other hand, the transmission signal is converted into an optical signal by the laser diode 64 in the ONU 9 for λ1, and the upstream optical signal (λ
1) 103, which is transmitted on the same line as the downstream optical signal (λ1) 101 using the waveguide type optical coupler 92,
It is transmitted to the same optical fiber transmission line 100 as the downstream optical signal (λ1) 101 using M91.

[0007] The ONU 10 for λ2 optically receives the downstream optical signal (λ2) 102 separated by the WDM 91 as the reception signal # 2 through the light receiving element 11 and the gate 12.

[0008]

In the above-mentioned conventional optical subscriber system, the above components, that is, WD
Since optical components such as M and PIN photodiodes and laser diodes are used, there is a problem that the presence of a plurality of optical components causes a bottleneck in the price of an ONU, which is required to be economical.

Therefore, an object of the present invention is to solve the above-mentioned problems and to reduce the number of optical components to be used.
It is an object of the present invention to provide an optical subscriber system capable of realizing an economical system and a two-way optical transmission system using the same.

[0010]

SUMMARY OF THE INVENTION An optical subscriber system according to the present invention includes an optical network unit for processing a transmission / reception signal transmitted through an optical fiber transmission line and uses an optical subscriber unit using a wavelength division multiplexing system. Means for receiving only an optical signal of a first wavelength, and a means for reflecting the optical signal of the first wavelength transmitted through the optical fiber transmission line, and Second wavelength longer than optical signal of wavelength
Means for passing an optical signal having a wavelength of

A bidirectional optical transmission system according to the present invention includes a center station and an optical network unit for processing transmission / reception signals transmitted between the center station via an optical fiber transmission line, and includes a wavelength division multiplexing system. Bidirectional optical transmission system comprising a plurality of optical subscriber systems using a system, wherein a semiconductor external modulation system capable of receiving only an optical signal of a first wavelength from the center station by applying a bias in advance. And a light having a second wavelength that reflects the first wavelength optical signal transmitted from the center station via the optical fiber transmission line and has a longer wavelength than the first wavelength optical signal. A grating fiber for passing a signal is provided in the optical network unit of each of the plurality of optical network systems.

That is, the bidirectional optical transmission system of the present invention can be used in an ONU of an optical subscriber system using a wavelength division multiplexing system by using only a grating fiber and a semiconductor external modulator as optical components to be used. , Laser diode, PIN photodiode,
Optical components such as optical waveguides can be omitted, and the economical ONU can be achieved.

More specifically, in the optical subscriber system of the present invention, the wavelength of an optical signal for bidirectional optical communication is λ1, the wavelength of an optical signal for distribution-only optical communication is λ2, and one Consider a system that provides services to subscribers using optical fibers. It is also assumed that the wavelength of λ2 is sufficiently longer than the wavelength of λ1.

The downstream optical signal λ1 from the center station is input to a semiconductor external modulator in the ONU of the subscriber's home. By applying a bias to the semiconductor external modulator in advance by a bias circuit, it is possible to receive the downstream optical signal λ1. Due to its characteristics, a semiconductor external modulator that can receive an optical signal having a wavelength of λ1 does not respond to an optical signal having a wavelength of λ2 which is sufficiently longer than the wavelength of λ1.

When transmitting an upstream optical signal, the center station λ
The laser for one is continuously emitted. Further, a grating fiber is provided behind the semiconductor external modulator in the ONU for λ1 at the subscriber's house so as to reflect only the laser beam having the wavelength of λ1 of the center station. In this state, if a transmission signal biased by a bias circuit is input to the semiconductor external modulator, the optical signal having the wavelength of λ1 from the center station and the reflected light λ1 from the grating fiber can be externally intensity-modulated. The reflected light from the grating fiber in the ONU for λ1 at home is directly transmitted as an upstream optical signal through the same optical fiber transmission line, so that the upstream optical signal can be transmitted to the center station.

On the other hand, since the grating fiber reflects only the wavelength of λ1, the optical signal of the wavelength of λ2 dedicated for distribution passes through as it is. Since the semiconductor external modulator for λ1 does not respond to the wavelength of λ2 which is sufficiently long, λ2 which has passed through the semiconductor external modulator and the grating fiber is used.
Can be received by the ONU for λ2.

Therefore, optical components such as a WDM, a laser diode, a PIN photodiode, and an optical waveguide which are usually used in the ONU of the optical subscriber system using the wavelength division multiplexing method are not required, and the economical use of the ONU can be achieved. Become.

[0018]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a bidirectional optical transmission system according to one embodiment of the present invention. In the figure, in a bidirectional optical transmission system according to an embodiment of the present invention, a center station 6 and an ONU (optical) for λ1 are used.
al Network Unit: an optical network unit 2, an ONU 3 for λ 2, a home network 4, and a subscriber home 1 equipped with a television 5 through an optical fiber transmission line 1.
00 and are connected.

The ONU 2 for λ1 is a semiconductor external modulator 21
, A bias circuit 22, gates 23 and 24, and a grating fiber 200. Also,
The ONU 3 for λ2 includes a light receiving element 31 and a gate 32.

The center station 6 sets the wavelength of the optical signal for bidirectional optical communication to λ1, and sets the wavelength of the optical signal for distribution-only optical communication to λ2.
Is transmitted to the subscriber's home 1, and the upstream optical signal (λ1) from the subscriber's home 1 is received. When the uplink signal (λ1) is received, the λ1 laser (not shown) of the center station 6 is made to emit light continuously.

The ONU 2 for λ1 installed in the subscriber's house 1 has a semiconductor external modulator 21 and a grating fiber 2
00 and a bias circuit 22. The semiconductor external modulator 21 optically receives the downstream optical signal (λ1) 101 and externally modulates the reflected light from the grating fiber 200.

The grating fiber 200 is provided behind the semiconductor external modulator 21 and reflects only an optical signal having a wavelength of λ1. An upstream optical signal (λ1) 103 is generated by reflecting the laser light for λ1 from the center station 1 that has passed through the semiconductor external modulator 21 by the grating fiber 200. The bias circuit 22 applies a bias voltage to the external semiconductor modulator 21 to receive the downstream optical signal (λ1) 101, and applies a bias voltage to input the transmission signal 111 to the external semiconductor modulator 21.

A light receiving element 31 is provided in the ONU 3 for λ2. The light receiving element 31 outputs a downstream optical signal (λ
2) optically receive 102;

FIG. 2 is a diagram showing characteristics (light absorption spectrum) of the semiconductor external modulator 21 of FIG. The operation of the bidirectional optical transmission system according to one embodiment of the present invention will be described with reference to FIGS.

The center station 6 sets the wavelength of the optical signal for bidirectional optical communication to λ1 and the wavelength of the optical signal for distribution-only optical communication to λ2.
Is transmitted to the subscriber's home 1, and the upstream optical signal (λ1) 103 from the subscriber's home 1 is received. It is also assumed that the wavelength of λ2 is sufficiently longer than the wavelength of λ1.

The downstream optical signal (λ1) 10 from the center station 6
1 is input to the semiconductor external modulator 21 in the ONU 2 for λ1 in the subscriber's house 1. Since the semiconductor external modulator 21 is preliminarily biased by the bias circuit 22, it is possible to receive the downstream optical signal (λ1) 101. From the characteristics shown in FIG. 2, the semiconductor external modulator 21 capable of receiving the optical signal of the wavelength λ1 does not respond to the optical signal of the wavelength λ2 which is sufficiently longer than the wavelength of λ1.

When transmitting the upstream optical signal (λ 1) 103, the laser for λ 1 of the center station 6 is made to emit light continuously.
Further, a grating fiber 200 is provided behind the semiconductor external modulator 21 in the ONU 2 for λ1 in the subscriber's house 1 so that only the laser light of the wavelength λ1 of the center station 6 is reflected.

In this state, when the transmission signal 111 biased by the bias circuit 22 is input to the semiconductor external modulator 21, the optical signal having the wavelength of λ1 from the center station 6 and the reflected light λ1 from the grating fiber 200 are output. External intensity modulation can be performed, and the reflected light from the grating fiber 200 in the ONU 2 for λ1 in the subscriber's home 1 becomes an upstream optical signal (λ1) 103 as it is, and is transmitted through the same optical fiber transmission line 1.
00 to be transmitted to the center station 6.

On the other hand, in the grating fiber 9, λ1
Is reflected, so that the optical signal of wavelength λ2 dedicated to distribution passes through as it is. As shown in FIG. 2, the semiconductor external modulator 21 for λ1 does not respond to the wavelength of λ2, which is sufficiently long, so that the optical signal of wavelength λ2 that has passed through the semiconductor external modulator 21 and the grating fiber 200 is λ2. Will be received by the ONU 3.

FIG. 3 is a configuration diagram showing a specific configuration example of the bidirectional optical transmission system according to one embodiment of the present invention. The figure shows a configuration example in the case where the number of subscriber homes in which the ONUs shown in FIG. 1 are installed is increased to m (m is a positive integer of 2 or more).

In the bidirectional optical transmission system according to one embodiment of the present invention, as shown in FIG.
By installing the × m optical coupler 7, the downstream signal is distributed to m subscriber homes 1-1 to 1-m. When the center station 6 receives an uplink signal, the center station 6 receives λ1
Laser for continuous emission, and the laser light is 1 ×
The optical signal is branched by the m optical coupler 7, and each of the subscriber's homes 1-1 to 1-1
The signal is reflected by the grating fibers (not shown) of the ONUs 2-1 to 2-m for -m of λ1 and transmitted to the center station 6 as an uplink signal.

As described above, optical components such as WDM, laser diode, PIN photodiode, and optical waveguide, which are generally used in the ONU of the optical subscriber system using the wavelength division multiplexing system, can be omitted. Can be reduced, and the ONU can be made more economical.

[0033]

As described above, according to the present invention, an optical subscriber system including an optical network unit for processing a transmission / reception signal transmitted through an optical fiber transmission line and using a wavelength division multiplexing system. A semiconductor external modulator capable of receiving only the optical signal of the first wavelength by applying a bias in advance, and reflecting the optical signal of the first wavelength transmitted through the optical fiber transmission line, and By providing the optical network unit with a grating fiber that transmits an optical signal of a second wavelength longer than the optical signal of the first wavelength, the number of optical components used can be reduced, ON
There is an effect that the economy of U can be achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a bidirectional optical transmission system according to one embodiment of the present invention.

FIG. 2 is a diagram showing characteristics (light absorption spectrum) of the semiconductor external modulator 21 of FIG.

FIG. 3 is a configuration diagram illustrating a specific configuration example of a bidirectional optical transmission system according to an embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a conventional bidirectional optical transmission system.

[Description of Signs] 1,1-1 to 1-m Subscriber's home 2,1-1 to 1-m ONU for λ1, 3,1-1 to 1-m ONU for λ2 4 Home network 5 Television 21 Semiconductor outside Modulator 22 bias circuit 23, 24, 32 gate 31 light receiving element 7 1 × m optical coupler 100 optical fiber transmission line 200 grating fiber

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04B 10/04 10/06

Claims (9)

[Claims] An optical subscriber system including an optical network unit for processing a transmission / reception signal transmitted via an optical fiber transmission line and using a wavelength division multiplexing method, wherein an optical signal of a first wavelength is provided. Means for receiving only the first wavelength, and a second wavelength having a longer wavelength than the first wavelength and reflecting the first wavelength optical signal transmitted through the optical fiber transmission line. Means for passing an optical signal of the optical subscriber line in the optical network unit. 2. The means for receiving only the optical signal of the first wavelength comprises a semiconductor external modulator capable of receiving only the optical signal of the first wavelength by applying a bias in advance. 2. The optical subscriber system according to claim 1, wherein the means for reflecting the optical signal of the first wavelength and transmitting the optical signal of the second wavelength comprises a grating fiber. 3. The optical network unit according to claim 2, wherein a light receiving element for receiving the optical signal of the second wavelength passing through the semiconductor external modulator and the grating fiber is included in the optical network unit. Optical subscriber system. 4. The semiconductor external modulator reflects the optical signal of the first wavelength transmitted through the optical fiber transmission line and the grating fiber when the biased transmission signal is input. 3. The optical fiber transmission line according to claim 2, wherein an upstream optical signal obtained by externally intensity-modulating the optical signal of the first wavelength is transmitted to the optical fiber transmission line.
Or an optical subscriber system according to claim 3. 5. A plurality of optical subscriber units using a wavelength division multiplexing system, including a central office and an optical network unit for processing transmission / reception signals transmitted between the center office via an optical fiber transmission line. A bidirectional optical transmission system comprising: a means for receiving only an optical signal of a first wavelength from the center station; and a means for transmitting the optical signal from the center station via the optical fiber transmission line. Means for reflecting the optical signal of the first wavelength and passing an optical signal of a second wavelength longer than the optical signal of the first wavelength. A bidirectional optical transmission system, which is provided in a subscriber line termination device. 6. The means for receiving only the optical signal of the first wavelength comprises a semiconductor external modulator which can receive only the optical signal of the first wavelength by applying a bias in advance. 6. The bidirectional optical transmission system according to claim 5, wherein the means for reflecting the optical signal of the first wavelength and passing the optical signal of the second wavelength comprises a grating fiber. 7. The optical network unit of each of the plurality of optical subscriber systems, comprising a light receiving element for receiving the optical signal of the second wavelength passing through the semiconductor external modulator and the grating fiber. 7. The bidirectional optical transmission system according to claim 6, wherein: 8. The optical signal of the first wavelength transmitted from the center station via the optical fiber transmission line at the time of inputting the biased transmission signal and the grating fiber. 8. An optical system according to claim 6, wherein an upstream optical signal obtained by externally intensity-modulating the optical signal of the first wavelength reflected by the optical fiber is transmitted to the center station via the optical fiber transmission line.
A two-way optical transmission system as described. 9. The bidirectional optical transmission system according to claim 8, wherein the center station includes a laser transmitter for the first wavelength that emits light continuously when the upstream optical signal is received.