Fiber-optic cable with adjustable dispersion and optical transmission system

 

(57) Abstract:

Symmetric fiber-optic cable with adjustable dispersion contains the first and second optical fibers. The first optical fiber is a conventional single-mode fiber and has a first effective area and a positive dispersion characteristic in the given working wavelength range. The first optical fiber is divided into two parts essentially the same length. The second optical fiber has a second effective area and a negative dispersion characteristic in the working wavelength range. The second fiber is a fiber with dispersion shifted or fiber non-zero dispersion, which have a negative dispersion and a small effective area. A second optical fiber connected between the two parts of the first fiber for receiving an optical cable with an average fully dispersed within the working range of wavelengths equal to essentially zero. Fiber optic cable can be embedded in the optical fiber transmission system, containing over optical unit and at least one regenerator. Reduced non-linear effects at large distances. 8 C.p. f-crystals, 1 tab., 2 Il.

Izobreteniyami dispersion and the system based on it.

Light signals transmitted by optical fibers, the influence of various nonlinear effects which cause distortion and attenuation, which limits the practical transmission range. Typically, the optical fiber used in fiber optic devices, which consist of optical terminal unit and multiple amplifiers/repeaters connected by optical fibers. Amplifiers/repeaters, which are usually placed at equal distances from each other along the path of propagation, serves to increase the intensity of the light pulses to compensate for the effects of attenuation. The total path length distribution is limited to phase shifts of the pulse signal resulting from the optical inhomogeneity of optical fibers.

The magnitude of nonlinear effects, affecting the transmission of a signal depends on various characteristics of optical fibers. One of the characteristics is "effective cross-sectional area" or simply "effective area" of the fiber. For an optical signal with a given energy density, the more effective area, the farther the signal can be passed through the fiber without significant losses. Thus, the use of amplifiers/repeaters as well as the length of the entire transmission system.

Another important characteristic of the optical fiber, which affects the signal propagation is its variance. To non-linear effects, which are particularly sensitive to fiber dispersion, are parametric processes, such as phase automodulation, cross-phase modulation and four-wave offset. Fiber dispersion causes the frequency broadening of the pulse signal along the path of propagation, this effect is cumulative and requires filtering of the signal before it is input to the receiver. Even after filtering, the extension of the received signal degrades the signal-to-noise ratio and increases the error in the signal. Thus, it is desirable to have close to zero dispersion characteristic in the working wavelength range of the optical system. A suitable range of wavelengths for transmission over long distances is between 1530 and 1560 nm.

Some industrial optical fibers is known as fiber dispersion-shifted, have zero dispersion around some suitable wavelength, for example of about 1550 nm. However, these fibers usually have a small effective area, which requires placed swesty as fiber non-zero dispersion also has a small effective area and a very small but not zero, the dispersion around 1550 nm. Other industrial optical fibers, such as conventional single-mode fibers have a larger effective area and a very strong dispersion around 1550 nm. Thus, a single optical fiber is usually not possible to combine the desired large effective area and the zero dispersion around especially suitable working range of wavelengths.

Fiber-optic system with "controlled dispersion" is a system containing an optical fiber with a positive dispersion characteristic, and an optical fiber with a negative dispersion characteristic in which the full dispersion is close to zero. For example, in "Kurtzke, Christian. Suppression of Fiber Nonlinearities by Appropriate Dispersion Management (Suppression of nonlinearities in the fiber by the appropriate governing dispersion), IEEE Photonics Technology Letters, 1993, vol. 5, pp. 1250-1253", which is incorporated in this description by reference, the proposed configuration, which uses alternating segments of optical fibers with relatively high chromatic dispersion, then positive, then negative. In "Chraplyvy et al. 8x10 Gb/s Transmission Through 280 km of Dispersion Managed Fibers (Peredannoe description by reference, the described transmission system, having an average dispersion around zero, in which each segment consists of a relatively short segment of a conventional fiber with a size dispersion of 16 PS/nm/km and longer fiber length with offset variance with the value of variance, equal to 2.5 PS/nm/km

In "Henmi et al. An Arrangement of Transmission-Fiber Dispersions for Increasing the Spacing Between Optical Amplifies in Lumped Repeater Systems (Distribution of the dispersion in the fiber is used for transmitting signals, to increase the spacing between optical amplifiers in systems with concentrated repeaters), ibid, pp.1337-1340", which is incorporated in this description by reference, a method for reducing non-linearity in the transmission system under which the fiber with a dispersion value of about of-0.2 PS/nm/km at a wavelength of 1,548 μm, attached to a short piece of fiber with zero dispersion at the wavelength of 1.3 μm, the complete dispersion of the plot is close to zero. A similar method is described in "Henmi et al. A New Design Arrangement of Transmission Fiber Dispersion for Suppressing Nonlinear Degradation in Long-Distance Optical Transmission Systems with Optical Repeater Amplifiers (the New distribution of the dispersion in the fiber is used for transmitting signals, to suppress related nelineinostyami), Journal of Lightware Technology, 1993, vol. 11, pp. 1615-1621", which is incorporated in this description by reference.

In U.S. patent N 5191631 described fiber-optic cable with adjustable dispersion containing the first single-mode optical fiber having a first effective area and a positive dispersion characteristic in the given working wavelength range, and a second optical fiber having a second effective area and a negative dispersion characteristic in the working wavelength range, and the first effective area than the second effective area. The first optical fiber in a predetermined operational range of wavelengths has an effective area substantially larger, and the variance, significantly smaller than the second optical fiber. The first optical fiber with a larger effective area and a positive dispersion characteristic is placed at the output terminal of the optical unit or repeater before the second optical fiber with a smaller effective area and a negative dispersion characteristic to reduce the effects of nonlinearity at large distances.

The optical transmission system known from the above patent contains a terminal op is a mini-cable.

In Fig. 1 shows an example of a known fiber-optic system 100 transfer. The system 100 includes a target optical unit 110 and the relay 120, known as "amplifiers/repeaters". The block 110 and the relay 120 is connected by two "asymmetric" fiber-optic cables 150 and 160. "Asymmetric" fiber optic cable 150 is used for transmission from block 110 to the relay 120, and fiber-optic cable 160 is used for transmission from the relay 120 to block 110. Each "asymmetric" fiber optic cable 150 and 160 consists of a relatively short portion 130 with a positive variance (+D) and large effective area, which is connected with the longer part 140 with negative dispersion (D) and a smaller effective area. Part 130 with a larger effective area is located at the beginning, that is, closer to the block 110 or the relay 120, to reduce the effects of nonlinearity at a greater distance. As part of the greater effective area should be near the transmitting unit 110 or the relay 120 for transmission in each direction between the block 110 and the relay 120 requires two "asymmetric" fiber optic cable 150 and 160. Duplication of the "asymmetric" velocityview initial manufacturing costs and complicates the current operation of the system 100.

The invention

Fiber-optic cable with adjustable dispersion according to the present invention contains the first single-mode optical fiber having a first effective area and a positive dispersion characteristic in the given working wavelength range, and a second optical fiber having a second effective area and a negative dispersion characteristic in the working wavelength range, and the first effective area than the second effective area. According to the invention, the specified first optical fiber includes two parts essentially the same length and said second optical fiber connected between the two parts of the specified first optical fiber, and the average total variance symmetric fiber-optic cable with adjustable dispersion within the working range of wavelengths equal to the first value of the average total variance, which is usually equal to essentially zero.

The second optical fiber is usually longer than any of the two parts of the specified first single-mode fiber, for example, the ratio of the length of any part of the first single-mode fiber to the length of the specified second optical fiber can the second optical fiber may have a total length of from 60 to 140 km

The first single-mode fiber preferably has an effective area in the range from 70 to 90 μm, and in the working wavelength range from 1530 to 1560 nm has a dispersion characteristic in the range from 15 to 20 PS/nm/km or from 0.1 up to 6.0 PS/nm/km

The second optical fiber typically has an effective area in the range from 45 to 55 μm2and is the fiber dispersion-shifted or fiber non-zero dispersion, in both cases with a negative dispersion and a small effective area.

Fiber optic cable can be included in the optical transmission system containing a target optical unit and at least one relay connected to the specified target optical unit optical cable made according to the invention.

Fiber-optic cable with adjustable dispersion according to this invention has several advantages. Such "symmetric" fiber-optic cable is easier to manufacture than the known cables, as it does not require complex design special "asymmetric" fiber-optic cable, which includes a separate optical fiber for transmission in opposite directions. "Symmetric"is m known cables, as for its manufacture are readily available optical fiber, and less complex structure allows to reduce the number of required optical fiber. Less complex design "symmetric" fiber-optic cable with adjustable dispersion, in addition, allows to simplify the development of fiber-optic systems. Although the "symmetric" fiber-optic cable with adjustable dispersion has a less complex structure than the known cables, it likewise helps to reduce nonlinear effects, as it also contains a segment of optical fiber with a large effective area on the output of each repeater or terminal optical unit that transmits the optical signal.

Brief description of drawings

In Fig. 1 depicts a block diagram of a known optical fiber transmission system with asymmetric location of fiber optic cables.

In Fig. 2 depicts a block diagram of an optical fiber transmission system with multiple fiber optic cables with adjustable dispersion according to this invention.

Detailed description of the invention

In Fig. 2 depicts a block diagram of an optical fiber system 120, also referred to as "amplifiers/repeaters", and "symmetric" fiber-optic cables 250 with adjustable dispersion. Fiber optic cable 250 with adjustable dispersion allows us to simplify the original manufacturer and the current operation of the system 200, as it eliminates the need for accommodation "asymmetric" fiber-optic cables for each direction between the block 110 and the relay 120 or between repeaters 120, as shown in Fig. 1.

Fiber optic cable 250 with adjustable dispersion, in addition, is cheaper to manufacture and operate than the known cables, because for its manufacture are readily available optical fiber, and less complex structure allows to reduce the number of required optical fiber. Although fiber optic cable 250 with adjustable dispersion has a less complex structure than the known cables, it likewise helps to reduce nonlinear effects, as it also contains a segment 230 of the first optical fiber with a large effective area on the output of each relay terminal 120 or the optical unit 110, the transmitting optical signal.

In Fig. 2 target optical unit is on, can operate as a receiver and receive optical signals from the repeater 120. The repeaters 120 receive the transmitted optical signal and then amplify, filter, and relay optical signals, the method known in the art. Fiber optic cable 250 with adjustable dispersion connects the block 110 with the repeater 120 and subsequent pairs of repeaters 120 with each other.

Fiber optic cable 250 with adjustable dispersion, also known as "cable retransmission interval contains a first optical fiber having two parts 230 and the second optical fiber 240. The first optical fiber from two parts 230 has a large effective area and a positive variance (+D) and is preferably a conventional single-mode fiber. In this particular embodiment, the first optical fiber has an effective area of approximately 70 to 90 μm2and the value of variance of approximately 15 to 20 PS/nm/km at the operating wavelength range from about 1530 to 1560 nm, while it can be an optical fiber with a different effective area and a different value of variance.

The second optical fiber 240 is typically a fiber with an offset of disperse the objective area. In this particular embodiment, a second optical fiber 240 is the value of variance of approximately minus 0.1 PS/nm/km to -6,0 PS/nm/km at the operating wavelength range from about 1530 to 1560 nm and an effective area of approximately 45 to 55 μm2though it may be used an optical fiber with a different effective area and a different value of variance.

Fiber optic cable 250 with adjustable dispersion is formed at the connection parts 230 of the first optical fiber with the second optical fiber 240. Fiber optic cable 250 with adjustable dispersion is constructed so that its full average variance within the working range of wavelengths equal to the desired value. In this particular embodiment, a desired average full variance approximately equal to zero in the working wavelength range, although there may be other values.

To obtain the "symmetric" fiber optic cable 250 with adjustable variance of the total length of parts 230 of the first optical fiber and second optical fiber 240 is chosen such that the total average dispersion fiber-optic cable 250 with adjustable variance was equal to the required in the kPa 240 is determined from the relationship of measures of dispersion parts 230 of the first optical fiber and second optical fiber 240. To determine the appropriate length of parts 230 of the first optical fiber and second optical fiber 240 may be taken into account also other factors such as the type of the target optical unit 110 and relay 120 used in the system 200.

In this particular embodiment, a two part 230 of the first optical fibers have essentially the same length, and their total length is substantially less than the length of the second optical fiber 240, although the total length of the portions 230 may be equal to or greater than the length of the second optical fiber 240, depending on the specific dispersion characteristics of the parts 230 of the first optical fiber and second optical fiber 240. In addition, in this particular embodiment, the ratio of the length of any portion 230 of the first optical fiber to the length of the second optical fiber 240 is in the range of from about 1:10 to 1:25, although this value may change if necessary. In addition, in this particular embodiment, a cable length 250 connecting block 110 with the repeater 120 or the relay 120 with another relay 120 is in the range of from about 60 to 140 km, although the full length of the cable 250 may also Kno simpler variant of the asymmetric arrangement of optical fibers for transmission in different directions between the block 110 and the relay 120 or between repeaters, it is shown in Fig. 1 as "symmetric" fiber-optic cable with adjustable dispersion can transmit in different directions with equal efficiency. Improved design of fiber-optic cable 250 with adjustable dispersion reduces the cost of manufacture and operation in comparison with the known cables, as the cable 250 is composed of readily available optical fibers, such as conventional single-mode fiber and the fiber dispersion-shifted or fiber non-zero dispersion. This uses fewer optical fibers, eliminating the need to install separate optical fibers for different directions. Although fiber optic cable 250 with adjustable dispersion has a simple structure, it allows to reduce non-linearity in the transmission in different directions, because the optical signal transmitted in different directions, always first passes through a portion 230 of the first optical fiber with a large effective area. Large effective area reduces heterogeneity.

Just to illustrate, the following are examples of systems with "symmetric" fiber-optic cable ale with adjustable dispersion at the operating wavelength of 1545 nm

Simulated system 200 with symmetrical optic cables 250 for a working wavelength of 1545 nm, containing terminal unit 110 and the relay 120, and a pair of relays 120, located at a distance of 120 km In this design as the second optical fiber 240 is used single-mode fiber with zero dispersion SMF-LSTMthe company Corning, which usually has an effective area of 55 μm2and variance -1,49 PS/nm/km at a wavelength of 1545 nm, and for parts 230 of the first optical fiber single-mode fiber SMF-28TMthe company Corning, which usually has an effective area of 80 μm2and variance 16,63 PS/nm/km at a wavelength of 1545 nm. When such measures of dispersion and the distance between the block 110 and the relay 120, and between the pairs of relays 120, the total length of the parts 230 is approximately 9.9 km (each part 230 is approximately 4.9 km) and the length of the second optical fiber 240 is equal to approximately 110,1 km.

As shown in the table. 1, at the working wavelength of 1545 nm full variance for the area from the terminal unit 110 and relay 120 and between the repeaters 120 is always essentially zero.

Therefore, the data table. 1 shows that when using the about to get the effective management of the variance.

This detailed description is provided only as an example. There are various changes that are within the essence and scope of the invention which is limited only by his formula.

1. Fiber-optic cable with adjustable dispersion containing the first single-mode optical fiber having a first effective area and a positive dispersion characteristic in the given working wavelength range, and a second optical fiber having a second effective area and a negative dispersion characteristic in the working wavelength range, and the first effective area than the second effective area, characterized in that the first optical fiber includes two parts essentially the same length and said second optical fiber connected between the two parts of the specified first optical fiber, moreover, the average total dispersion fiber-optic cable with adjustable dispersion within the working range of wavelengths equal to the first value of the average total variance.

2. Fiber-optic cable under item 1, characterized in that the first value is the average of the full dispersion is essentially zero.

3. Fiber two parts specified first single-mode fiber.

4. Fiber-optic cable under item 3, characterized in that the ratio of the length of any part of the first single-mode fiber to the length of the specified second optical fiber is in the range from 1 : 10 to 1 : 25.

5. Fiber-optic cable under item 1, characterized in that the two portions of the said first single-mode fiber and the specified second optical fiber have a total length of from 60 to 140 km

6. Fiber-optic cable under item 1, characterized in that the said first single-mode fiber has an effective area in the range from 70 to 90 μm2.

7. Fiber-optic cable under item 1, characterized in that the said first single-mode fiber in the working range of wavelengths from 1530 nm to 1560 nm has a dispersion characteristic in the range from 15 to 20 PS/nm/km or 0.1 to -6,0 PS/nm/km

8. Fiber-optic cable under item 1, characterized in that the second optical fiber has an effective area in the range from 45 to 55 μm2.

9. Fiber-optic cable under item 1, characterized in that the second optical fiber is a fiber with dispersion shifted or fiber non-zero dispersion.

10. Optical specified target optical unit optical cable, characterized in that the optical cable made in accordance with any of paragraphs.1-9.

 

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SUBSTANCE: branded optical fiber has optical-fiber core, marking layers, and dyed layer. Set of marking layers composed of small definite-size droplets of marking dye are disposed at intervals along optical fiber core, on its surface. Dyed layer is applied to marking layers and to optical-fiber core on areas covered with marking layers. Specified thickness of dyed layer is not less than or equal to 2 μm and not more than or equal to 10 μm. Specified thickness of marking layers is not less than or equal to 0.5 μm and not more than or equal to 2.5 μm. Specified length of marking layers is not less than or equal to 1 mm and not more than or equal to 15 mm. Interval between marking layers should be specified between 1 and 200 mm. Specified volumetric efficiency of marking layers should be mot over or equal to 20%. Specified diameter of small droplets should be not less than or equal to 10 μm. and not less than or equal to 10 μm. Optical cable has plurality of branded fibers disposed in forming tube covered with plastic jacket.

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12 cl, 4 dwg

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18 cl, 6 dwg

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