MXPA97003742A - Opt network - Google Patents

Abstract

A redóptica comprising an end head station (1) connected to a plurality of red optic units through a fiber optic network having a plurality of separation levels, wherein a separation level is constituted by a repeater n: 1 (3) provided with means of verification (10, 11) for the scale and leveling of transmissions of the red optic units.

Description

OPTICAL NETWORK DESCRIPTION OF THE INVENTION This invention relates to an optical network. Currently, in the United Kingdom, the telecommunications network includes a main line network, which is substantial and completely constituted by an optical fiber, and a local access network, which is substantially and completely made up of copper pairs. In the future, it could be highly desirable to have a fixed, elastic, transparent telecommunications infrastructure all the way to the premises of the customers, with the capacity of predictable service requirements, or at least in points (for example, re & triction) closer to the premises of the clients. One way to achieve this, could be to create a fiber network fully managed for access topography. An attractive option for this is an optical branch access network, such as passive optical networks (PON), which incorporate an individual fiber optic and no active electronic bandwidth limiting. In a PON, an individual fiber is fed from an end head (changer), and is deployed through passive optical separators in cabinets and distribution points (DP) to optical power network (ONU) units. The UN can be in customer premises, or on the street serving ~ a number of clients. The use of optical separators allows sharing the feeder fiber and the exchange-based optical line termination (OLT) equipment, thus giving cost advantages in PON. Currently, the preferred option is the simple deployment of PON, that is, PON are supplied upstream and downstream separately, so that each customer has two fibers. Although simple work increases the complexity of the infrastructure due to the two fibers per circuit required, it has benefit from a low optical insertion loss [due to the absence of duplex couplers) and a low loss of return, since such systems they are insensitive to reflections less than 25dBm with separate transmission and reception trajectories. However, duplex PONs where a single fiber carries traffic in both directions are also possible. Typically, a PON has a four-way separation followed by an eight-way separation, so that an individual end-head fiber can serve up to 32 clients. In a known arrangement, TPON (telephony over a passive optical network) "an end-head station broadcasts time division frames to all terminations in the network. The transmitted frames include traffic data as control data. Each termination recognizes and responds to appropriately directed portions of data in the broadcast frames, and ignores the rest of the frames. In the upstream direction, the transmission is through the time division multiple access (TDMA), where each termination transmits data in a predetermined period, so that the data of the different terminations are assembled in a TDMA format frame. predetermined. The applicant has developed a bit transport system (BTS) for use in a PON that operates using TDMA. The BTS are described in the European patent specifications 318331, 318332, 318333 and 318335. A necessary aspect for such a network is the provision of compensation for the different delays and attenuations associated with the different distances of the various terminations of the head station. extreme. Up to this point, each termination is arranged to transmit a controlled scale pulse to arrive at a respective determined portion of the upstream TDMA frame. The end head station is arranged to verify time control, i.e., the phase and amplitude of the pulse arrival of each of the terminations, and to return servo-control signals to the terminations to delay or advance your transmissions as appropriate, and to adjust your arrival energy. This scaling and leveling procedure is particularly important during the fixation of a PON system, or when a PON system is improved, or when a PON system is returned for use after a fault has been repaired. In such cases, the scaling and leveling procedure takes a finite time (all travel delay), which depends on the distance from the end-head station to the terminations. This travel delay of the terminations towards the end head station and back to the terminations to effect the scaling and leveling is known as the dead zone. This is because the dead zone represents the time during which the PON clients can not obtain any service since PON is being used exclusively for scaling and leveling. For a simple PON of the type described above, where an end-head station is connected up to 32 terminations over a distance typically of 6-8 km, the dead zone is only 60-80 meters, and this does not represent a major problem . However, recently, the PON principle has been expanded to form what is known as the Super PON concept, where high-power optical amplifiers are used to allow very large, high separation PONs to be developed. For example, the use of optical amplifiers (such as fiber amplifiers) allows up to 3,500 clients to be connected to a single end-station at distances of up to 200 km. In this case, the dead zone is of the order of 1 meter to 2 meters, and this gives rise to a significant loss of service to the customers of such SuperPON. Unfortunately, optical amplifiers can only be used in a downstream SuperPON, since the use of amplifiers in an upstream SuperPON could cause noise problems resulting in superimposed amplified stimulated emissions (ASEs) of the amplifiers. One way to provide amplification in an upstream superPON is to replace the last level of separation (i.e., the level of separation closest to the end head) through a repeater. This device converts optical input signals to electrical signals. It amplifies them, and converts the amplified electrical signals to optical signals for transmission. It should be noted that such networks are usually referred to as PON, although they may include electronic amplification and, therefore, strictly speaking, they are not "passive". The present invention provides an optical network comprising an end-head station connected to a plurality of optical network units through an optical fiber network having a plurality of separation levels, wherein a level of separation in the direction Upstream is constituted by a repeater n: l provided with inspection means to vary and level transmissions of the optical network units. Preferably, the repeater is connected to the end head station through an individual optical fiber. Typically, such an individual optical fiber has a length of up to 200 km (for example from 100 to 200 km) and the optical network units are separated from the repeater at distances of up to about 8 km. In a preferred embodiment, the repeater includes n receivers and a transmitter, the transmitter is connected to the end head station, and each of the receivers is connected to a respective optical fiber, which is part of the network between the repeater and the optical network units. Conveniently, the repeater can be provided with a multiplexer for multiplexing signals received by the receivers for transmission to the end-head station through the transmitter, and with monitoring means for verifying the functions of the receivers., the multiplexer and the transmitter. Preferably, each receiver is constituted by a pair of parallel receiver boards, and the transmitter is constituted by a pair of parallel transmitter boards. In this case, the supervising means can be such in order to disconnect one of the receiver boards of each pair of its associated optical fiber and to connect the other reception board of that pair of optical fiber at the moment of detection of a failure in the receiver board, and is in order to disconnect one of the transmitting boards of the individual fiber optic and to connect the other transmitter board to the individual fiber optic at the moment of detecting a fault in the transmitter board. In another preferred embodiment, the repeater is constituted by a plurality of repeater modules, each of which is connected to an individual optical fiber leading to the end head station. For example, each repeater module may include a plurality of receivers and a transmitter, the transmitter is connected to the individual optical fiber, and each of the receivers are connected to a respective optical fiber forming part of the network between the repeater and the Optical network units, the arrangement is such that the toteil number of receivers in the repeater modules is equal to n. Each repeater module may be provided with a multiplexer to multiplex the signals received by the receivers of that module for transmission to the end-head station through the associated transmitter, and with monitoring means to verify the functions of the associated receivers, the associated multiplexer and the associated transmitter. Preferably, each receiver is constituted by a pair of parallel receiver boards, and each transmitter is constituted by a pair of parallel transmitter boards. In this case, the supervising means of each repeater module can be such that one of the receiving boards of each associated pair of its associated optical fiber is disconnected and to connect the other receiving board of that pair of optical fiber after the detection of a failure in the receiver board, and is such that it disconnects one of the associated transmitter boards of the individual fiber optic and to connect the other transmitter board of that pair to the signal optical fiber after the detection of a fault in the transmitter board. A SuperPON incorporates a leveled and leveled repeater constructed in accordance with the invention, it will now be described in greater detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic representation of the SuperPON; Figure 2 is a block diagram of the SuperPON repeater; Figure 3 is a block diagram of a receiving board that forms part; of the repeater of Figure 2; and Figure 4 is a schematic representation of a SuperPON including several repeaters. With reference to the drawings, Figure 1 shows a SuperPON having an end-head station 1 connected to a plurality of ONUs (not shown) via an individual fiber 2, a repeater 3 and a network 4 (shown schematically) including two or more levels of separation. The SuperPON displayed in an upstream SuperPON, that is, is a simple network that carries ONU signals to the endpoint station 1. A. Downstream PON is also assumed to be present to carry signals from the end head station to the ONU, although it is not shown in the drawings; although the invention can also be applied to PON duplex, if desired. Typically, the distance between the end head station 1 and the repeater 3 is on the 100 km to 200 km scale. The SuperPON is ready to use the BTS. The repeater 3 (see Figure 2) replaces the last separation level of a normal upstream SuperPON, that is, the level of separation closest to the endpoint station 1, the other separation levels are formed by the optical separators passive, in a conventional way. This last level of separation is 12: 1, so that the repeater 3 connects the individual fiber 2 of the end-head station 1 to twelve fibers 5 (only two of these are shown) forming part of the network 4. Each of fibers 5 carries a TDMA traffic at 155 Mbit / s, and fiber 2 carries a traffic at 1860 Mbit. The repeater 3 includes twenty-four receiver boards 6, which are connected in pairs to the twelve fibers 5. A receiver board 6 of each pair, forms a backup for the other receiver of that pair, thus providing a one-to-one receiver protection for each of the fibers 5. The repeater 3 also includes a transmitter / packer block 7 for packaging and transmitting data coming from the fibers 5. In order to provide one-to-one transmitter protection, the block 7 includes two transmitter / packer devices. A multiplexer / supervisor block 8 is placed between the receiver boards 6 and the block 7. The multiplexer of the block 8 ultiplexes the signals of the twelve active receiver boards 6 before these signals are packed and transmitted by the block 7; and the supervisors control the scaling and leveling functions of the repeater (as described below). Any convenient method for multiplexing on fiber 2 can be used; it is not necessary to follow the TDMA framework used in the fibers 5.

Each receiver board 6 (see Figure 3) is constituted by a receiver chip 9 of 155 ~ Mbits / s, an ASIC 10 scale, an ASIC leveling 11, a supervisor chip 12, a 16-bit 16-bit microcontroller chip, a packer chip / unpacker 14, an interface for multiplexer chip 15, and a power control chip 16. Chips 9, 14 and 15 are connected together through a common high-speed data connection 17, and all chips 9-16 they are connected together through a common low data rate control connection 18. The receiver chip 9 of the receiver board 6 receives data signals from its input fiber 5, and transfers this data to the packer / unpacker chip 14 and to the interface to the multiplexer chip 15 via the common high-speed data connection 17. The interface to the multiplexer chip 15 is connected to the blocking multiplexer 8, and the packer / unpacker chip 14 filters any operation signal and maintenance (O &M) and passes them to the 16-bit microcontroller chip 13. The O &M signals are sent regularly from the ONUs (every n BTS frame), and it is important to prevent these O &M signals from being returned to the end-head station in a SuperPON, since the end-head processing could be overexperated under certain problematic situations. In this way, the repeater 13 is effective to carry out the control of the O & amp;; M which are usually carried by the end station station of a PON. The scale of ASIC 10 and leveling of ASIC 11, under the control of the 16-bit microcontroller chip 13, performs the scaling and leveling functions, normally performed on the end head of a PON. In this way, the ASIC 10 scale and the ASIC 11 leveling check the time control, that is, the phase and amplitude of the arrival of the UN scale pulses, and the return of the servo control signals to the ONU. to delay or advance their transmissions as appropriate, and to adjust their arrival power. Since there is a fixed delay between repeater 3 and endpoint station 1, the only question that arises in the scale and leveling of delays between ONUs and repeater 3. However, since network 4 is such that The ONUs are typically 6-8 km from the repeater 3, the dead zone for the scale and the leveling is only 60-80 meters, and in this way does not cause problems. Here again, therefore, an important control function has been taken by the repeater 3 of the end-head station 1. The return of these servo-control signals is preferably transmitted from the repeater, at link 2, to the end head 1 and then later by the end head through PON downstream towards the ONUs.

The supervisor chip 12 checks the functions of the receiver chip 9, the multiplexer of block 8 and the transmitter of block 7, and is effective for switching the receiver board in pairs 6, if a problem is perceived with its receiver board. In that way, the receiver boards 6 are in pairs to have a redundancy of 1: 1 with a heat arrest. The rapid switching between the two receiver boards 6 of each pair, possibly without loss of service, helps with the identification of faults on the distribution side (ie, the downstream side of repeater 3) of the SuperPON. In other words, the supervisors chip 12 can be used to identify faults in parts of the network associated with specific fibers 5. This allows the remedial work to be performed on the fault branch without having to interrupt the entire SuperPON. This may be contrary to the known SuperPON that does not require a complete interruption for the eradication of faults. Similarly, the two transmitters of block 7 have a redundancy of 1: 1 with a heat arrest. Alternatively, the load can be interspersed between the two transmitters, so that, if one fails, the other takes the load from the transmitter with failure. The 16-bit microcontroller chip 13 controls the other chips 9-12 and 14-16, and the power control chip 16 controls the power supplied to the other chips. Figure 4 shows a modified form of the upstream SuperPON, where an end head station 21 is connected to three repeaters 23a, 23b and 23c through a single fiber 22. The repeater 23a is equivalent to the repeater 3 of Figure 1, since it is located between 100 km and 200 km from the end head station 21. The repeaters 23b and 23c are, however, located much closer to the end head station 21. A respective PON 24a , 24b and 24c is associated with each of the repeaters 23a, 23b and 23c. In this case, the three repeaters 23a, 23b and 23c collectively constitute the final separation of the upstream SuperPON, that is, they provide a distributed repeater function where, the repeater 23a has six pairs of receiver boards (not shown, but similar to the receiver boards 6 of Figure 2), and the repeaters 23b and 23c each have three pairs of receiver boards. Obviously, each of the repeaters 23a, 23b and 23c has a transmitter / packer block (not shown, but similar to block 7 of Figure 2) having two transmitter / packer devices to provide transmitter protection from one to the other. one, and a multiplexer / supervisors block (not shown, but similar to block 8 of Figure 2). This type of SuperPON, which has a distributed repeater function, is suitable for more rural areas of the country, where customers are more widely separated. In addition to this distributed repeater function, the embodiment of Figure 4 works in the same way as Figure 1. The repeaters 23a, 23b and 23c can be as parts of an individual repeater forming the last separation level of the upstream SuperPON ( although the first two repeaters 23a and 23b are attached to the main fiber 22 leading to the end head station 21 through the separators 25a and 25b, respectively). In this way, each of the repeaters 23a, 23b and 23c controls the scaling and leveling functions for its own PON 24a, 24b and 24c. As the dead zone in each of these PONs 24a, 24b and 24c is only of the order of 60-80 meters (the PONs are such that their ONUs are only 6-8 km from their repeaters 23a, 23b and 23c), this does not It gives rise to a significant loss of service for customers of this type of SuperPON. However, it is noted that if the repeaters are located at different distances from the end head and the TDMA is used in this part of the network, then a scaling and leveling function must be provided (either on the repeaters or in the end head) to carry to scale and level the part of the net in the end head and the repeaters. Alternatively, the link of the repeater (or repeaters) to the end head by itself can be part of a separate PON with its scale and leveling facilities. This separate PON may be a conventional PON, or one in accordance with the present invention. It should be evident that the type of repeater with scale and level described above, greatly reduces the dead zone in an upstream SuperPON. In addition, by varying and leveling the receiver of the repeater, the power of the system is reduced, that is, the requirements of scale sensitivity and dynamic receiver are reduced. In this way, in the SuperPON upstream of the prior art, it is necessary to combine, in the end-head receiver, up to 3500 client signals, and this leads to the problem of additive noise. By moving the scaling and leveling function downstream to the repeater, the number of clients to be addressed is reduced to 288 per receiver board 6, and this leads to a reduction in the required power. In addition, each of the receiver boards 6 only needs to represent signals coming from the ONU at distances of up to 6-8 km, and this leads to the reduction in dynamic scale requirements. With a reduced dynamic scale, it should be possible to consider the implementation of the system without any leveling. In this case, the receiver boards 6 of the repeaters can be simplified. Another advantage of using the scale and level repeater type described above is that the upstream data rate can be as high as 300 Mbps (which is the maximum for upstream normal SuperPON). This is because each of the twelve branches that lead to a repeater can carry 300 Mbits / s, and the data streams can be multiplexed for inward transmission. The advantage of this is that a SuperPON can now offer the same bit rate of 1.2Gbits / s in both upstream and downstream directions. Other advantages of this arrangement are the greater flexibility in the link for the end-head station, since the distribution and transport sections of the SuperPON are separated, so that it is possible to double-connect sections of the PON to two or more end-head stations. Also, O &amp message filtering; M by the repeater has the advantage of avoiding overload in the end head station. A further advantage, particularly with the embodiment of Figure 4, is the adaptation of temperature changes. In this way, BTS normally verifies the temperature changes, verifying the variant pulses in the head of pack ends, the appropriate correction signals that are sent to the ONU when the temperature changes are perceived. In this regard, it should be noted that, with a long-range PON, the temperature change that will displace the data by one bit is as low as 0.075 ° C. This temperature verification function can, however, be performed only where there is no overlap of bits from different clients. This overlap of bits is a function of the distance between the ONUs of the clients and the verification center. In this way, when this type of repeater is used to verify ONU for distance only of up to 6-8 km, there is considerably less chance of bit overlap of the different clients, and the verification and correction of the improved temperature can be achieved.

Claims (10)

1. An optical network comprising an end-head station connected to a plurality of optical network units through an optical fiber network having a plurality of separation levels, characterized in that the level of separation in the upstream direction is constituted by a repeater n: l provided with verification means for the scale and leveling transmissions of the optical network units.

2. The optical network according to claim 1, characterized in that the repeater is connected to the end head station through an individual optical fiber.

3. The optical network according to claim 2, characterized in that the individual optical fiber has a length of up to 200 km, and the optical network units are separated from the repeater at distances of up to about 8 km.

4. The optical network according to any of claims 1 to 3, characterized in that the repeater includes n receivers and a transmitter, the transmitter is connected to the end head station, and each of the receivers is connected to an optical fiber. which is part of the network between the repeater and the optical network units.

5. The optical network according to claim 4, characterized in that the repeater is provided with a multiplexer for multiplexing signals received by the receivers for transmission to the end head station through the transmitter.

6. The optical network according to claim 1, characterized in that the repeater is constituted by a plurality of repeater modules, each of which is connected to an individual optical fiber that leads to the end head station.

7. The optical network according to claim 6, characterized in that each repeater module includes a plurality of receivers and a transmitter, the transmitter is connected to an individual optical fiber, and each of the receivers is connected to a respective optical fiber that forms As part of the network between the repeater and the optical network units, the arrangement is such that the total number of receivers in the repeater modules is equal to n.

8. The optical network according to claim 7, characterized in that each repeater module is provided with a multiplexer to multiplex the signals received by the receivers of that module for transmission to the end-head station by the associated transmitter.

9. The optical network according to claims 4, 5, 10 or 11, characterized in that the repeater is provided with monitoring means for verifying the functions of the receivers, the associated multiplexer and the associated transmitter.

10. The optical network according to claim 9, characterized in that each receiver is constituted by a pair of parallel receiver boards, each transmitter is constituted by a pair of parallel transmitter boards, and the means of supervisors of each repeater module are such that they disconnect one of the receiver boards of each associated pair of its associated optical fiber and connect the other receiving board of said pair to the optical fiber after the detection of a fault in the receiver board, and are such that they disconnect one of the associated transmitter boards of the individual fiber optic and connect the other transmitter board of that pair to the fiber optic signal after the detection of a fault in the transmitter board.