RU2187896C1 - Optical terminal of atmospheric laser communication line - Google Patents

Abstract

FIELD: communications engineering; single-span wireless communication lines. SUBSTANCE: optical terminal accommodates only optical receiving and transmitting centers joined with their respective interfaces through optical connectors; used as transmitting and receiving feeders are optical cables connected to optical connectors of optical terminal. EFFECT: eliminated impact of external actions and electromagnetic fields on system parts. 2 dwg

Description

 The invention relates to atmospheric laser information transmission systems and can be used as a single-span wireless communication line or lines with receptions, as a relay line, and also as a backup section in case of breakages or repair of fiber-optic communication systems.

 Known optical terminal devices for atmospheric laser communication lines manufactured by AstroTerra Corporation (USA), LSA Photonics (USA), Cable free Solutions Ltd (United Kingdom). These devices are a block in which both electronic nodes and quantum-optical transmitting and receiving modules are located, as well as optical transmitting and receiving nodes. See US patents 539268A from 05/03/1994, H 04 B 10/12, US 5335109A from 02/08/1994, H 04 B 10/12; DE 3834821 A1 from 05/03/1990, H 04 B 10/12; EP 559352 A1 of 11.29.1993, H 04 B 10/12; FR 2732813A1 dated 04/04/1996; H 04 V 10/12; DE 4029559 A1 dated 03.19.1992. The last of these patents is the closest analogue of the proposed device.

 Known terminal optical devices located on the roof of a tall building (or tower, or other object of sufficient height), inside the hermetically sealed enclosure, contain electronic and quantum-optical transmitting and receiving modules, while the transmitting quantum-optical module is paired with a transmitting optical unit (collimator ), and the receiving quantum-optical module - with a receiving optical lens, electrical information signals (at the transmitting electronic unit and, accordingly, the electric signal from the receiving electronic node) are transmitted via coaxial cable (feeder) to the building premises, in which the transmitting and receiving equipment of the plesiochronous digital hierarchy (PDI) or synchronous digital hierarchy (SDH) is located. In the same bundle in which the aforementioned coaxial cables are located, the electric power cable of the nodes of the terminal optical device is also located.

 The main disadvantages of the known optical terminal devices of atmospheric laser lines are as follows. For communication, an optical terminal device containing electronic and quantum optical modules is installed in open space. Moreover, all components of the device, including particularly sensitive quantum-optical modules, are exposed to the external environment, in particular temperature (see A.S. Nemirovsky. Communication systems and radio relay lines. M .: Communication, 1980 p.376-377.) In addition, the optical terminal device is exposed to electromagnetic interference (including coaxial cable 5).

 The listed disadvantages of the known optical terminal devices must also include the following. An electronic digital signal (or analog) from the electrical joints of the PDI (PDH) or SDH (SDH) equipment, which can be placed on the first floors (1st or 2nd) of a building with a height of 40-50-100 m or higher, is supplied, as already noted, using a coaxial cable. As you know, modern coaxial cables have a bandwidth of not more than 1000-2000 MHz per km and attenuation of the order of 10 dB. At the same time, modern SDH equipment is designed for transmission speeds of 155 Mbit / s, 622 Mbit / s, 2.5 Gbit / s, 10 Gbit / s and 40 Gbit / s (i.e., respectively, STM-1, STM-4, STM-16, STM-64 and STM-256). It follows that the known optical terminal devices of laser atmospheric lines are limited by the transmission speed at best at the STM-4 level, which significantly narrows the scope of their application. It should also be noted that the large attenuation of the signal introduced by the coaxial cable and the limited bandwidth of it do not allow the optical terminal device to be located at distances of more than 500-1000 m from the SDH equipment.

 The technical result of the proposed terminal device of the laser atmospheric line is as follows: 1) to exclude the influence of the external environment on the electronic and quantum-optical modules; 2) eliminate the effect of electromagnetic interference on these modules, as well as the feeder; 3) to exclude the dependence of the length of the feeder on the speed of information transfer; 4) to ensure the applicability of the proposed device for all transmission speeds from 2 Mbit / s to 40 Gbit / s.

 The technical result is achieved by the fact that in the optical terminal device of the laser atmospheric communication line only optical receiving and transmitting nodes are located, paired with fiber-optic joints (interfaces), which are optical connectors (transmitting and receiving), to which respectively transmitting and receiving feeders are connected made of fiber optic cables. Using these feeders, the transmitting and receiving optical signals are fed to the optical joints of the transmitting and receiving quantum optical modules, respectively, located together with the PDI or SDH equipment in the building.

 Comparative analysis with the prototype shows that the claimed optical terminal device of the laser atmospheric communication line, unlike the prototype, does not contain electronic and quantum-optical modules in its housing and consists only of optical and fiber-optical elements, and the receiving and transmitting feeders are fiber optic cable. Thanks to this embodiment of the optical terminal device of the laser atmospheric line, the goal is achieved, namely: 1) the electronic and quantum-optical modules are not exposed to environmental influences - temperature and humidity; 2) the effect of electromagnetic interference is excluded; 3) the dependence of the location of the optical terminal device on the information transfer rate is excluded, since the optical fiber has an almost unlimited bandwidth, 4) extremely small losses (0.2 dB / km at a wavelength of 1.55 μm and 0.5 dB / km at wavelength 1.3 μm) allow you to place the optical terminal device at a distance from the equipment of the PDI or SDH for units or even tens of kilometers.

 The above allows us to conclude that the claimed device meets the criteria for inventions of "novelty" and "significant differences".

In FIG. 1 presents a diagram of the inclusion of the proposed optical terminal device of the laser atmospheric line, where:
1 - the housing of the optical terminal device;
2 - optical connectors (transmitting and receiving);
3 - optical cable (2 fiber);
4 - receiving optical node;
5 - transmitting optical node;
6 - transmitting (BOOSTER) and receiving (PREAMPLIFIER) optical amplifiers, coupled respectively to the optical joints of the transmitting and receiving quantum-optical modules, the electrical joints of which are connected to the corresponding electrical joints of the PDI or SDH equipment;
7 - PDI or SDH equipment;
8 - power supply and control units.

In FIG. 2 shows a device of the proposed optical terminal device, where:
9 - the housing of the optical terminal device;
10 - optical cable receiving feeder;
11 - optical connector receiving and optical node;
12 - receiving optical node;
13 - optical cable transmitting feeder;
14 - optical connector of the transmitting optical node;
15 - optical transmitting node (collimator).

 The electrical interface of the transmitting equipment PDI or SDH is connected to the input electrical interface of the quantum optical module (figure 1), the optical output interface of which is connected to the input optical interface of the optical power amplifier 6 (figure 1). The output interface of this amplifier using an optical cable (transmitting feeder) 3 (Fig.1) is connected to the optical connector 2 of the transmitting optical node 5 of the optical terminal device. The receiving optical node 4 of this device by means of a second (receiving) optical connector 2 is connected to the optical input interface of the optical receiving amplifier 6 (Fig. 1) (preamplifier) by the optical cable 3 (receiving feeder), the output optical interface of which is connected to the input optical receiving quantum optical module. The output electrical interface of this module is connected to the input electrical interface of the PDI or SDH 7 equipment.

 In FIG. 2, the receiving optical node 12 is connected to the input end of the optical connector 11, the output of which is connected to the optical connector of the receiving feeder - the optical cable 10. From the side of the transmitting path, the optical cable 13 of the transmitting feeder is connected to the transmitting optical connector 14, which is interfaced with its output end to the transmitting optical node 15 (collimator).

 The principle of operation of the optical terminal device is as follows. From the optical output interface of the SDH 7 equipment (Fig. 1), an optical digital signal is input to the optical power amplifier 6 (Fig. 1). From the output optical interface of this amplifier, a power-amplified optical digital signal is transmitted through the transmission feeder 3 (Fig. 1) to the transmitting optical unit 5 via the optical connector 2. Since the core of a single-mode fiber has a diameter of ~ 10 μm, the end of this fiber can be considered practically, a point source of light. This end is paired with the input focus of the transmitting optical unit 5, which is a collimator. At this node, the transmitting optical digital stream increases in diameter to several tens of millimeters, and its divergence decreases to several angular minutes. This optical energy flow is directed along the atmospheric transmission path. On the receiving side, the optical digital stream coming through the atmosphere from the other end enters the receiving optical node 4 (Fig. 1), at the output focal point of which there is the center of the input end of the optical cable 10 (Fig. 2). A receiving optical feeder (Fig. 2), which is an optical cable 10, is connected to this OB through an optical connector 11. The other end of this receiving feeder, which is inserted into the building, is connected to the input interface of the optical receiving amplifier 6 (Fig. 1). From the optical output of this amplifier, the optical digital stream enters the optical input interface of the SDH equipment (6) (Fig. 1). Note that the use of an optical amplifier in transmission (booster) allows you to raise the power level of the optical signal to + 30-36 dB • m (i.e. 1-4 W), and the use of an optical amplifier in reception (preamplifier) allows you to increase the sensitivity of reception to level - 56 dB • m (2.048 Mbit / s) ... 26 dB • m (2.5 Gbit / s). Both of these factors make it possible to ensure the energy potential of the line up to 92 - 62 dB depending on the transmission speed and provide the required reliability with the estimated line length. If the specified reliability is not ensured with the calculated length of a single-span line, then the atmospheric line can be implemented when organizing a re-receiving amplification point by installing an optical amplifier in a nearby room. In this case, the optical signal received from this end of the line is transmitted through OK to the input of the optical amplifier, amplified and then fed through the optical cable to the transmitting connector of the transmitting node 14 (Fig.2). The use in an optical terminal device of a laser atmospheric communication line of only optical nodes and standard optical connectors and optical cables allows us to obtain not only the advantages mentioned above, but additional advantages. These additional advantages are that standard equipment with optical interfaces designed for fiber-optic cable communication systems (FOCL) can be used as PDI and SDH equipment. At the same time, if the structure of this equipment includes optical amplifiers (booster and amplifier), then in this case additional optical amplifiers are not needed. In addition, in cases where the length of the atmospheric line (path) is not more than 500 m, optical amplifiers are not necessary, even if they are not part of the standard equipment of PDI and SDH, because the output optical power of standard equipment without optical amplifiers is quite large and amounts to an average of 1 mW (0 dB • m).

 Thus, the proposed optical terminal device of the laser atmospheric communication line can improve not only the technical parameters, but also significantly reduce the cost of the device.

Claims (1)

 An optical atmospheric laser terminal device comprising a receiving optical node, a transmitting optical node, and receiving and transmitting optical amplifiers, characterized in that on the front panel of the optical terminal device housing there are receiving and transmitting optical nodes connected via optical connectors to fiber optic cables connected respectively to the receiving and transmitting optical amplifiers located outside the housing of the optical terminal device

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