JP3222407B2 - Subscriber premises optical communication system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an FTTH (Fi
The present invention relates to a subscriber premises optical communication system corresponding to an optical fiber network called “ber To The Home”.

[0002]

2. Description of the Related Art For high-speed telephone communication, FTTH is being realized as a communication network using optical fibers to homes. In response to this, studies on the optical system for subscriber premises for this FTTH are in progress. In the optical network system for subscribers toward FTTH, the transmission speed is 156M.
bps. As a desired subscriber optical communication system, a plurality of terminal units are connected to each other so that one terminal unit can be provided in each room.
It is important to be able to connect to the line telephone line. Also, it is desired that the bus in the house be about 100 m.

[0003] As this kind of optical communication system at the subscriber's premises, for example, IEICE Transactions B-1 Vol. J72-BI
There is a system shown in No.11 pp.961-969. In this proposed system, an optical passive bus network is configured as a topology, but extension communication and collision control are actively controlled using a network terminating device.

[0004]

However, in the case of the above-mentioned proposed system, the bus length is limited by the round-trip propagation delay time difference. The transfer efficiency is reduced by the round-trip propagation delay time difference. Therefore, there is a disadvantage that the reception levels are different. It is necessary to use an active device to implement extension communication and collision control.

In general, a configuration using a passive element has high reliability and requires no maintenance. However, in the case of an active device as described above, since the reliability is low, periodic maintenance or maintenance is required. However, there is a problem that it is not suitable as a subscriber home system.

In view of the above, an object of the present invention is to provide a subscriber premises optical communication system which is highly reliable and does not require maintenance.

[0007]

In order to solve the above-mentioned problems, in a subscriber optical communication system according to the present invention, a wavelength of an optical reception signal from an access network is set to a first wavelength of an optical reception signal in the subscriber's home. Wavelength conversion for converting the wavelength of the optical transmission signal in the subscriber premises at the second wavelength λ2 different from the first wavelength λ1 into the wavelength of the optical transmission signal through the access network. Means, one end terminal portion composed of two optical input / output terminals, and the other end terminal portion composed of n (n is an integer of 2 or more) or more optical input / output terminals. Optical coupling between a first optical coupling element that propagates a signal, one end side terminal section including n or more optical input / output terminals, and the other end side terminal section including one optical input / output terminal A second optical coupling element for propagating an optical signal according to First and second optical modulators for generating two optical transmission signals, an optical output terminal provided on the output side of the first optical modulator, and an optical signal from the second optical modulator An optical input / output terminal to which is supplied, a first optical receiver for the wavelength λ1 and a second optical receiver for the wavelength λ2, which receive an optical signal input from the optical input / output terminal;
And n terminal units for detecting, using the first light receiver and the second light receiver, a transmission signal from another terminal unit or an optical signal from the access network. And a terminal inside the subscriber's home of the wavelength conversion means and one of two input / output terminals of one end side terminal portion of the first optical coupling element are optically connected, and the second One of the input / output terminals of the other end terminal portion of the optical coupling element and the other of the two input / output terminals of the one end terminal portion of the first optical coupling element are optically connected to each other; The optical input / output terminals of the terminal units are optically connected to any one of the n or more optical input / output terminals of the other end side terminal portion of the first optical coupling element, and the n terminal units The light output terminal of the second optical coupling element has n or more light input terminals at the one end side terminal portion. Characterized in that either the force terminal is optically connected.

[0008]

In the subscriber optical communication system according to the present invention, the received signal arriving through the access network is converted into the received signal wavelength .lambda.1 in the subscriber premises by the wavelength converting means, and the first optical coupling is performed. It is supplied to the input / output terminal of the terminal on one end side of the element. Then, the data is input to each terminal unit in the subscriber's house from the input / output terminal of the other end side terminal portion of the first optical coupling element. Each terminal unit receives this optical reception signal at the first receiver for the wavelength λ1.

[0009] The optical transmission signal from the terminal unit is converted to a wavelength λ2 by the second modulator, and is input to the wavelength conversion means through the first optical coupling element. Then, the wavelength is converted into a wavelength to be transmitted through the access network by this wavelength conversion means and output to the access network.

At the time of this transmission, for example, prior to the transmission, an optical transmission signal of wavelength λ2 is supplied from the first modulator to the second optical coupling element through an optical output terminal. This second
The optical signal of the wavelength λ2 through the optical coupling element is input to all the terminal units through the first optical coupling element.
Then, in the terminal unit, this is received by the second light receiver for the wavelength λ2, and based on the received signal, an optical transmission signal from any terminal unit is detected with respect to the access network, and collision is prevented.

In an extension call between terminal units, the wavelength λ from the first modulator of the terminal unit on the transmitting side is used.
The second optical transmission signal is transmitted through the optical output terminal → the second optical coupling element → the first optical coupling element → the optical input / output terminal of the terminal unit → the second optical receiver and the second optical receiver. The light is received by the light receiver and an extension call is made.

As described above, according to the present invention, an optical communication system at the subscriber's premises that enables collision prevention and extension calls can be configured by using only passive elements without using active elements.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a subscriber premises optical communication system according to the present invention;

FIG. 1 shows an entire optical network system of this embodiment, which is an ONU (Optical Network) connected to an optical fiber access network 3.
kUnit; an optical access device) 1 and a maximum of n (n is an integer of 2 or more) terminal units 2 connected to the ONU 1 respectively.

The ONU 1 comprises a wavelength converter 11, a 2: n star coupler 12, and an isolator 13.

The wavelength converter 11 converts an optical signal having a wavelength λi arriving through the access network 3 into a wavelength λ1 of an optical reception signal for the subscriber premises and an optical transmission signal from the terminal unit 2 in the subscriber premises. Wavelength λ2 of the access network 3
To a wavelength λo for transmission through

2: The n-star coupler 12 bidirectionally transmits and receives optical signals between each of the two optical input / output terminals on one end and each of the n optical input / output terminals on the other end. Is what you do. This 2: n star coupler 12
A first optical coupling element is configured.

The isolator 13 is for transmitting an optical signal only in a direction indicated by an arrow in the drawing. In this example, between each of the n optical input / output terminals at one end and one optical input / output terminal at the other end for receiving optical signals from n terminals, It gives and receives.
Although not shown, this isolator 13 has a 1: n
It has a built-in star coupler. This isolator 13 constitutes a second optical coupling element.

In the ONU 1, one end on the access network side of the wavelength converter 11 is connected to an optical fiber cable connected to the access network 3, and the other end is 2: n.
One of the two optical input / output terminals on one end of the star coupler 12 is connected to an optical fiber made of, for example, a plastic fiber.

2: n at the other end of the n-star coupler 12
Each of the optical input / output terminals is an optical fiber cable 3
1 is connected to an optical input / output terminal (terminal interface) 20 of the terminal unit 2.

Each of the n optical input / output terminals at one end of the isolator 13 of the ONU 1 is connected to an optical output terminal (terminal interface) 29 of the terminal unit 2 through an optical fiber cable 32. One optical input / output terminal on the other end side of the isolator 13 is 2: n
The star coupler 12 is connected to the other of the two light input / output terminals on one end by, for example, a plastic fiber. The optical fiber cables 31 and 32 also use plastic fibers.

Each of the terminal units 2 includes an optical input / output terminal 20, a light source 21 having a wavelength λ2, first and second optical modulators 22 and 23 for transmitting signals, and an isolator 2
4, a light receiver 25 for the wavelength λ1, a light receiver 26 for the wavelength λ2, optical couplers 27 and 28 for optical branching, and an optical output terminal 29. The connection between the respective optical passive elements in the terminal unit 2 is as follows:
For example, it is performed by a plastic fiber.

As the light source 21, in this embodiment,
An LED (light emitting diode) is used. This is in consideration of good connection with plastic fiber and safety in a system intended for ordinary households. In other words, when looking into the light source direction from the fiber end face, if a laser light source was used as the light source,
There is a risk that laser light with high coherence and high optical power may enter the eyes. However, in the case of LEDs, the optical power is not as large as that of a laser, and the light emitted from the end face becomes scattered light, which is safe. It is. In addition, there is an advantage that the LED has a long life.

The light from the light source 21 is
7 and supplied to the first and second optical modulators 22 and 23, where the light is modulated and the wavelength λ
2 optical transmission signals are obtained. The first optical modulator 22 is a subscriber premises modulator, and the second optical modulator 23
Is an optical modulator for access network. First optical modulator 22
Are connected to the light output terminal 29. Also, the second
The output terminal of the optical modulator 23 is connected to the optical input / output terminal 20.

The light input / output terminal 20 is connected to the light receiver 25 and the light receiver 26 through an optical coupler 28. The optical receiver 25 is for receiving an optical signal transmitted through the access network 3 having the wavelength λ1. Also,
The light receiver 26 is for receiving an optical signal propagated between the terminal units 2 in the subscriber's house having the wavelength λ2, and recognizes that another terminal unit 2 is in use to perform collision prevention control, It is used for receiving an optical reception signal during an extension call.

The transmission / reception of the optical signal through the access network 3 and the collision control of the use between the terminal units 2 at that time in the subscriber optical communication system of the present embodiment, The operation of extension communication between the two will be described.

The optical transmission signal of the wavelength λi transmitted from the destination through the access network 3 is converted by the wavelength converter 11 into an optical reception signal of the reception wavelength λ1 in the subscriber's house. The optical reception signal of wavelength λ1 from the wavelength converter 11 is input to the optical input / output terminals 20 of all terminal units 2 through the 2: n star coupler 12.

In each of the terminal units 2, the optical reception signal of the wavelength λ1 is split by the optical coupler 28 and input to the photodetectors 25 and 26, but is detected only by the photodetector 25 for the wavelength λ1. That is, the fact that the signal is a received signal from the access network 3 is detected by a difference in wavelength from a transmitted signal of wavelength λ2 from another terminal unit.

On the other hand, in this optical network system, transmission from the terminal unit 2 is performed as follows.

First, the other terminal unit 2 is notified that the call is to be transmitted. This notification signal (wavelength λ2) is generated and transmitted by the first modulator 22 of the terminal unit that performs transmission. Then, this notification signal is transmitted to the isolator 13
And 2: input to another terminal unit through the n-star coupler 12. In each terminal unit, the notification signal is received by the receiver 26, and an acknowledgment signal is sent back. In the terminal unit that performs the transmission, the receiver 26 receives this acknowledged signal through the modulator 22 → isolator 13 → 2: n star coupler 12 and confirms it in the same manner as described above.

Then, after confirming the acknowledged signal, in the terminal unit that performs transmission, an optical transmission signal is generated by the modulator 23 and optically transmitted from the optical input / output terminal 20 to the 2: n star coupler 12 through the isolator 24. Send a signal. In the ONU 1, the optical transmission signal is supplied to the wavelength converter 11 through the 2: n star coupler 12, converted into a signal of the wavelength λo to the access network 3, and transmitted to the access network 3.

In the same manner as the exchange of the notification signal for preventing collision before transmission and the acknowledgment signal,
An extension call between the terminal units 2 is also performed.

As described above, in this embodiment, the optical communication system at the subscriber's premises, which can prevent the collision of the transmission from the terminal unit and can make an extension call, is constituted by using all the optical passive elements. Can be. in this way,
By all using optical passive elements,
Low power consumption, high reliability, and easy maintenance of the system. Further, in the above-described embodiment, since a long-life LED is used as the light source in the terminal unit 2, reliability is high in this respect as well, and as described above, security is high as a home system.

Since the star coupler is used, it is possible to insert and remove the terminal unit during operation of the system, and to connect a spare fiber for the terminal unit to the ONU1.
The terminal units can be easily added to the terminal units.

Further, in the above-described embodiment, since the plastic fiber is used as the optical connection means between each element, the system can be constructed at low cost in combination with the use of the LED as the light source. it can.

[0036]

As described above, according to the present invention, it is possible to prevent a collision at the time of use between a plurality of terminal units and to enable an extension call by using only a passive element without using an active element. An optical communication system can be configured. For this reason, a system with low power consumption, high reliability, and easy maintenance can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a subscriber optical network according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 ONU 2 Terminal unit 3 Access network 11 Wavelength converter 12 2: n star coupler 13 Isolator 21 Light source 22, 23 First and second modulator 24 Isolator 25 Receiver for λ1 26 Receiver for λ2 27, 28 Optical coupler

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-8-274787 (JP, A) JP-A-8-331163 (JP, A) JP-A-4-207646 (JP, A) JP-A-61- 30139 (JP, A) JP-A-5-191358 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 10/00-10/28 H04J 14/00-14/08 H04L 12/46 H04L 12/66

Claims (1)

(57) [Claims] 1. A wavelength of an optical reception signal from an access network is converted into a first wavelength λ1, which is an optical reception signal wavelength in a subscriber's premises, and a second wavelength λ2 different from the first wavelength λ1. Wavelength conversion means for converting the wavelength of the optical transmission signal in the subscriber's premises into the wavelength of the optical transmission signal through the access network; one end terminal portion comprising two optical input / output terminals;
Is an integer of 2 or more) and a first optical coupling element that propagates an optical signal by optical coupling between the optical input and output terminals and n or more optical input / output terminals. Between the one end terminal portion and the other end terminal portion including one optical input / output terminal.
A second optical coupling element that propagates an optical signal by optical coupling; first and second optical modulators for generating the optical transmission signal having the wavelength λ2; and an output side of the first optical modulator , An optical input / output terminal to which an optical signal from the second optical modulator is supplied, and a first for the wavelength λ1 for receiving an optical signal input from the optical input / output terminal. A light receiver and a second light receiver for the wavelength λ2, respectively, and using the first light receiver and the second light receiver, a transmission signal from another terminal unit or from the access network. And n terminal units for detecting whether or not the optical signal is the optical signal. A terminal inside the subscriber's house of the wavelength conversion means, and a terminal part on one end side of the first optical coupling element. One of the output terminals is optically connected to the other end of the second optical coupling element One of the input / output terminals of the terminal unit is optically connected to the other of the two input / output terminals of the one end side terminal of the first optical coupling element; The output terminal is optically connected to any one of n or more optical input / output terminals of the other end side terminal portion of the first optical coupling element, and the optical output terminals of the n terminal units are Second
Wherein the optical coupling element is optically connected to any one of the n or more optical input / output terminals of the one end side terminal section.