CN100454788C - A passive optical network - Google Patents

Abstract

The invention provides a passive optical network, comprising: an optical line terminal, an optical splitter and an optical user end, characterized in that it also includes an optical amplifier, one end of which is connected to the optical transmission output end of the optical line terminal, and one end is connected to The optical combiner end of the optical splitter is used to amplify the optical transmission signal of the optical line terminal; a high-sensitivity optical detector, one end is connected to the receiving end of the optical line terminal, and the other end is connected to the optical combiner of the optical splitter. The road end is used to receive the uplink optical signal from the optical user end to the optical line terminal. The passive optical network also includes a wave splitter/multiplexer, one end of which is respectively connected to the optical amplifier and the high-sensitivity photodetector, and the other end is connected to the optical combiner end of the optical splitter for coupling Input and output optical signals. The invention can greatly increase the number of optical branches, thereby increasing the number of users accessing the passive optical network and reducing the average access cost of users.

Description

A passive optical network

technical field

The invention relates to passive optical network technology, in particular to a passive optical network capable of increasing the number of access users.

Background technique

PON (Passive Optical Network) technology is a very promising technology for optical access now and in the future. FTTH (Fiber to the Home), FTTB (Fiber to the Building), FTTC (Fiber to the Community), etc. will all adopt passive optical network technology in large numbers.

Please refer to Figure 1, the passive optical network receives signals from the OLT (optical line terminal), and distributes them to each ONU/ONT (optical user end) through the ODN (optical splitter), and the ONU/ONT at the user end selectively receives the OLT Data signals, and then each ONU/ONT sends signals to the OLT in a time-division multiplexed manner. The optical splitter can realize the functions of optical splitting and optical combining. Its application greatly reduces the use of optical fibers and the number of active terminals, and reduces the cost of each user's access to the network.

Theoretically, the more splits the optical splitter has, the lower the average access cost per user. But in fact, when the number of optical splitters increases, the optical splitter will reduce the optical power of each splitter path and the optical power from each splitter path to the optical line terminal. Please refer to Figure 2. In the figure, 0 is the optical combiner end, and 1 ~N is the optical branch end, the light is input from the 0 end, and then output from the 1~N end, the light can also be input from the 1~N end, and output from the 0 end. The split ratio can be specified arbitrarily. For an evenly divided optical splitter of the usual fusion fiber process, its input and output insertion loss is about:

10LgN+a(dB);

Among them, a=0.5～2dB,

That is, when N=16, insertion loss=13~14dB.

According to the principle of the above-mentioned optical splitter, the larger the number of optical splitters, the smaller the optical power received by each optical user end and optical line end due to optical loss. When the optical power is less than the sensitivity of optical reception, the optical receiving end The optical signal cannot be received correctly, thus limiting the number of splits of the optical splitter.

In order to increase the number of branches of the optical splitter and reduce the cost of user access to the network, the prior art often uses a high-sensitivity optical detector at the optical receiving end of the ONU/ONT to receive optical signals.

Please refer to FIG. 3 , in order to increase the number of splits of the optical splitter, in the prior art, an APD (optical avalanche detector) is often used at the optical receiving end of the optical user end to receive optical signals. Since the sensitivity of APD light receiving is much higher than that of PIN (ordinary photodetector) (8~10db), and considering that the optical loss will increase by 3~4db every time the optical splitter is doubled, the use of APD will be higher than When PIN is used, the number of optical branches is increased by about 8 times. For example, in the GPON system, when the access distance is 20km, it usually only supports 32 branches. By using APD, the number of optical branches can reach more than 256.

Disadvantages of prior art:

Although the number of optical splits can be increased by using the optical avalanche detector APD at the optical receiving end, this solution requires the use of an APD at each optical network user end, and the network therefore increases a large amount of APD usage. Due to the APD The price is far more expensive than the price of PIN, so the cost of the whole system has also become very expensive. According to preliminary estimates, after using APD, the access cost of each user will increase by 500-700 yuan, so the average access cost of users cannot be reduced. cost purposes.

Contents of the invention

The purpose of the present invention is to provide a passive optical network system that can effectively increase the number of access users, this system can increase the ability of a single optical line terminal to access the number of users, and overcome the existing technology to increase the number of optical splitters In order to reduce the average access cost of optical network users, the problem of high cost will be generated when the number of splits is increased.

In view of the above purpose, the present invention provides such a passive optical network (PON), including an optical line terminal (OLT), an optical splitter (ODN), an optical user terminal (ONU/ONT), and the passive optical network also include:

An optical amplifier, one end is connected to the optical transmission output end of the optical line terminal, and the other end is connected to the optical combiner end of the optical splitter, for amplifying the optical transmission signal of the optical line terminal;

A high-sensitivity optical detector, one end is connected to the receiving end of the optical line terminal, and the other end is connected to the optical combiner end of the optical splitter, for receiving the uplink optical signal from the optical user end to the optical line terminal.

The above-mentioned passive optical network may also include a splitter/multiplexer, one end of which is respectively connected to the optical amplifier and the high-sensitivity optical detector, and the other end is connected to the optical combiner end of the optical splitter for coupling input , The output optical signal.

The beneficial effect that the present invention produces:

By adopting a reasonable configuration of passive optical devices in the passive optical network system, an optical amplifier and a high-sensitivity optical detector are included between the system optical line terminal and the physical connection of the optical distribution network, so that the passive optical network system The ability to access the number of users of a single optical line terminal in the network is enhanced, which solves the problem of the application bottleneck of the number of optical branches in the passive optical network in the prior art, thereby effectively reducing the average access cost of a single user;

At the same time, due to the use of the splitter/combiner, the passive optical network structure according to the present invention is suitable for both the dual-fiber transmission system and the single-fiber transmission system.

Description of drawings

FIG. 1 is a schematic structural diagram of a passive optical network;

Fig. 2 is a schematic diagram of an optical splitter;

FIG. 3 is a schematic diagram of a passive optical network structure using an APD in the prior art;

FIG. 4 is a schematic structural diagram of a passive optical network according to the present invention;

Fig. 5 is a schematic structural diagram of another passive optical network according to the present invention.

Detailed ways

The specific embodiments of the present invention will be described in further detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described here are only used to explain the present invention, and are not intended to limit the present invention.

The realization idea of the present invention is based on a reasonable configuration of optical devices. By configuring optical amplifiers, high-sensitivity photodetectors or devices that complete the first two functions in the passive optical network system, an optical line terminal connected The number of users is greatly increased, and the access cost shared by the system to each user is also reduced.

Please refer to FIG. 4 , which is a schematic structural diagram of a passive optical network produced according to the present invention. A passive optical network, including an optical line terminal, an optical splitter, and an optical user end, and also includes:

An optical amplifier, connected to the optical transmission output end of the optical line terminal, the use of the optical amplifier can amplify the direct optical transmission signal of the optical line terminal, and the optical gain provided by the optical amplifier makes the optical user The receiving power is improved, so it can meet the requirement of obtaining more branch numbers under the condition of the minimum optical power of optical receiving. For example, the direct optical transmitting power of the optical line terminal laser is usually -7~3dBm. After using EDFA, the optical output power can be Reach 17~22dBm, optical power gain can reach 10~20dB;

A high-sensitivity optical detector, connected to the receiving end of the optical line terminal, is used to receive the upstream optical signal from the ONU/ONT to the OLT. The high-sensitivity photodetector can use APD. By using APD, the sensitivity of the light receiving end can be improved. For example, when receiving a 1.25Gb/s data optical signal, the receiving sensitivity of the PIN detector is -24dBm, but the APD detector The receiving sensitivity is about -35dBm, and the use of APD improves the light sensitivity ability by about 10dB;

When the passive optical network is to achieve single-fiber transmission, please refer to Figure 5, the passive optical network also includes:

A multi-wavelength demultiplexer/combiner, the sub-ports of the multi-wavelength demultiplexer/combiner are respectively connected to the transmitting and receiving two wavelength signals of the optical line terminal, and the composite end of the multi-wavelength demultiplexer/combiner contains optical The two-wavelength signals transmitted and received by the line terminal, through the use of splitter/combiner, enable the multiplexing transmission of multiple optical signals in one optical fiber.

In the above passive optical network system structure, the optical gain generated by the optical amplifier is greater than 10dB, and the optical gain of the optical avalanche detector is about 10dB, that is, the optical gain in both directions is higher than 10dB. Therefore, the system in the optical line Under the same optical receiving effect of the terminal, the ability of optical splitting can be improved. According to the loss estimation formula: 10LgN+a, when the optical splitter increases the number of splits by 8 times, the loss will increase by 9dB. Therefore, based on comprehensive calculation, the system can increase the number of branches by 8 times. That is to say, the system that originally had 32 branches can achieve 256 branches after adopting this solution, but the entire network does not have a large increase in optical avalanche. The usage of detectors is reduced, so the average access cost of users is greatly reduced.

In the above passive optical network system, there is no restriction on the use of PIN or APD for optical reception at the ONU/ONT end, but the use of PIN is more conducive to reducing the cost of the passive optical network system.

In the above passive optical network system, the optical amplifier can be placed at any position between the optical transmitting end of the optical line terminal and the optical splitter.

In the above-mentioned passive optical network system, when EDFA is applied, it can be placed in the optical network terminal equipment, or in the optical splitter equipment, or even any possible position between the two.

The environment in which the above-mentioned passive optical network structure is applied includes passive optical network systems of various transmission data formats and management communication methods, such as ATM passive optical network, BPON, EPON and GPON and other passive optical networks.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of the claims of the present invention.

Claims (7)

1. A passive optical network comprising an optical line terminal, an optical splitter and an optical user end, characterized in that it also includes: An optical amplifier, one end is connected to the optical transmission output end of the optical line terminal, and the other end is connected to the optical combiner end of the optical splitter, which is used to amplify the optical transmission signal of the optical line terminal; A high-sensitivity optical detector, one end is connected to the receiving end of the optical line terminal, and the other end is connected to the optical combiner end of the optical splitter, for receiving the uplink optical signal from the optical user end to the optical line terminal. 2. The passive optical network according to claim 1, characterized in that: the passive optical network further comprises a demultiplexer/multiplexer, one end of which is respectively connected to the optical amplifier and the high-sensitivity optical detector, The other end is connected to the optical combiner end of the optical splitter for coupling input and output optical signals. 3. The passive optical network according to claim 1 or 2, characterized in that the optical amplifier is a semiconductor optical amplifier or a praseodymium-doped fiber amplifier or an erbium-doped fiber amplifier. 4. The passive optical network according to claim 1 or 2, characterized in that the high-sensitivity optical detector is an optical avalanche detector. 5. The passive optical network according to claim 1 or 2, characterized in that: the optical signal receiver at the optical user end is a photodiode receiver or a high-sensitivity optical detector. 6. The passive optical network according to claim 1, characterized in that: the optical amplifier can be arranged in the optical line terminal equipment or in the optical splitter equipment or in any possible position between the two . 7. The passive optical network according to claim 1, characterized in that the passive optical network can be applied to passive optical network systems of various transmission data formats and management communication methods.

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