JP2009204490A - Coated optical fiber comparison method and coated optical fiber comparison device - Google Patents

Abstract

The present invention provides a method of contrasting a core and a device for contrasting a core capable of reliably performing a contrast on an optical fiber with a small bending loss.
A method for contrasting single-mode optical fibers with reduced bending loss, characterized in that the test wavelength is shorter than the effective cutoff wavelength of the optical fiber. A transmission unit having a light source for injecting test light into an optical fiber, a core line control unit for generating leakage light by bending a desired position of the optical fiber into which the test light is incident, and a light receiving element for detecting the leakage light A device for contrasting cores, comprising: a light source capable of performing the method of contrasting a core of the present invention; and a core contrast unit.
[Selection] Figure 1

Description

  The present invention relates to an optical fiber core contrast method, and more particularly to a core contrast method and a core contrast device capable of reliably performing a core contrast on an optical fiber having a small bending loss.

  The core-line contrast technology for avoiding erroneous connection or disconnection of the optical fiber at the time of laying or service-in of the optical fiber has become important as the FTTH (Fiber to the home) technology expands. The core control is usually performed by bending the core wire and detecting the leak test light in a state where the test light is incident on the work target core wire.

  Conventionally, techniques disclosed in, for example, Patent Document 1, Non-Patent Document 1, and the like are known as optical fiber core contrast methods and apparatuses.

On the other hand, in recent years, a large number of single-mode optical fibers with a bending loss reduced compared to conventional ones have been developed in order to realize space-saving wiring in homes and high-density mounting on optical fiber cables (for example, non-patented). Reference 3 and Non-Patent Document 4).
JP 2003-65894 A http://www.fujikura.co.jp/Light_com/1020/sokutei.html, http://211.125.78.50/news/0510/news5.html Katsuaki Suzuki et al., NTT Technical Journal 2007.4, pp.54-55 ITU-T Recommendation G.657 (2006) S. Matsuo, et. Al, IEICE TRANSACTIONS on Electronics, Vol.E88-C, No.5, pp.889-895 (2005) Ohm, “Optical Fiber” (Okoshi / Okamoto / Hodate) J. Sakai and T. Kimura, Appl.Opt., Vol. 17, no. 10, pp. 1499-1506 (1978)

  However, when optical fibers having a small bending loss are subjected to optical fiber contrast, naturally, light leakage due to bending applied during optical fiber contrast is reduced. Therefore, there is a problem that it becomes difficult to control the cords.

  On the other hand, for example, Non-Patent Document 2 improves the light receiving sensitivity of the leaked light by improving the structure of the leaked light receiving unit. However, there is a limit to this prior art, and it is difficult to control the core for low bending loss optical fibers such as those disclosed in Non-Patent Document 3 and Non-Patent Document 4 in which bending loss is further reduced. was there.

  In addition, there is a high possibility that the bending loss of the fiber will be further reduced in the future, and there is a demand for a method capable of performing the core contrast with higher sensitivity.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a core wire contrast method and a core wire contrast device capable of reliably performing a core wire contrast on an optical fiber having a small bending loss.

  In order to achieve the above object, the present invention provides a method of contrasting a single-mode optical fiber with reduced bending loss, wherein the test wavelength is shorter than the effective cutoff wavelength of the optical fiber. To provide a method for contrast control.

  In the cord control method of the present invention, it is preferable that the test wavelength is set to a wavelength at which the bending loss of the higher-order mode of the measured fiber is reasonably large.

  In the cord control method of the present invention, the higher order mode is preferably an LP11 mode.

  In the cord contrast method, it is preferable to set the bend diameter and wavelength of the cord contrast portion so that the LP11 mode bend loss at the test wavelength is 0.1 dB / 180 ° or more.

  In the core wire contrast method of the present invention, it is preferable that an optical fiber whose bending loss of the fundamental mode at a signal wavelength is 0.1 dB / turn or less when wound once to a diameter of 30 mm is a measurement object.

  In the cord control method of the present invention, the test wavelength is preferably selected from 400 nm to 1260 nm.

  In the cord control method of the present invention, it is preferable that the test wavelength is selected from 600 nm to 1240 nm.

  In the cord control method of the present invention, the test wavelength is preferably 633 nm, 808 nm, 850 nm, 980 nm, or 1060 nm.

  In the core wire contrast method of the present invention, it is preferable that the test wavelength is selected from 860 nm to 1240 nm.

  In the cord control method of the present invention, it is preferable that the bend diameter of the cord control portion is in the range of 5 mm to 60 mm.

  In the cord contrast method of the present invention, it is preferable that the test light is modulated and the modulated signal is detected by the receiving unit.

  In addition, the present invention also detects a transmitter having a light source for injecting test light into an optical fiber, a core-line control unit for generating leaked light by bending the desired position of the optical fiber into which the test light is incident, and the leaked light. A core line contrast device including a light receiving element having a light receiving element that includes a light source and a core line contrast unit capable of performing the core line contrast method according to claim 1. A cord contrast device is provided.

The method for contrasting cores of the present invention makes it possible to use a higher-order mode for contrasting cores by setting the test wavelength to a wavelength shorter than the effective cutoff wavelength of the optical fiber. In addition, since the bending loss at the core contrast wavelength can be set independently of the bending loss in the fundamental mode, clearer core contrast is possible.
In addition, by setting the test wavelength to a wavelength at which the bending loss of the higher-order mode of the fiber to be measured is reasonably large, an appropriate amount of test light can be leaked by bending, and the cords can be compared.
Further, the higher-order mode is the LP11 mode, and by performing the core line contrast in the LP11 mode, the wavelengths of the signal light and the test light can be made close, and the core line contrast in the low-loss wavelength range is possible. . As a result, long-distance cords can be controlled.
In addition, by setting the bending diameter and wavelength of the core wire contrast portion so that the bending loss of the LP11 mode is 0.1 dB / 180 ° or more, a sufficient amount of leakage light can be obtained, and the heart clearly Line contrast can be performed. .
Moreover, the core wire contrast method of the present invention can measure an optical fiber whose bending loss in the fundamental mode at the signal wavelength is 0.1 dB / turn or less when wound once to a diameter of 30 mm.
In addition, by setting the test wavelength in the range of 400 nm to 1260 nm, preferably in the range of 600 nm to 1240 nm, it is convenient for carrying out the cord contrast method of the present invention.
In addition, if the test wavelength is any one of 633 nm, 808 nm, 850 nm, 980 nm, and 1060 nm, an existing inexpensive laser diode (LD) can be used, so that an inexpensive cord contrast device can be provided.
In addition, by setting the test wavelength in the range of 860 nm to 1240 nm, it is possible to use a wavelength different from the communication wavelength used in ITU and the like, and it is a wavelength region in which a higher mode exists, and there is no influence on transmission. Line contrast can be realized efficiently.
Moreover, if the bending diameter of the core wire contrast portion is in the range of 5 mm to 60 mm, an appropriate amount of leakage light is generated, and detection becomes easy.
Further, the test light is modulated, and the modulated signal is detected by the receiving unit, so that only the test light can be detected, and the core contrast can be performed with higher sensitivity.

  As described above, light leakage due to bending loss of the optical fiber is used for the core wire control. In the present invention, the optical fiber to be subjected to the cord contrast is a fiber with reduced bending loss.

  An optical fiber used for communication is usually single mode at a communication wavelength (see, for example, ITU-T Recommendation G. 652-657). This is because if there are a plurality of modes including higher-order modes at the communication wavelength, high-speed and large-capacity communication becomes impossible due to the influence of mode dispersion.

  On the other hand, from the viewpoint of fiber design, the fact that the communication wavelength is single mode means that the communication wavelength is longer than the effective cutoff wavelength of the higher-order mode (next to the fundamental mode) of the fiber. In other words, it can be paraphrased. The description of the cutoff wavelength is detailed in Non-Patent Document 5 and the like.

  Conversely, this indicates that at a wavelength shorter than the effective cutoff wavelength of a single mode fiber, the fiber can propagate a plurality of modes.

The bending loss in each mode is often expressed by a function such as a difference in propagation constant between the mode and the clad mode and electric field distribution (see Non-Patent Document 6). Therefore, the bending loss of each mode takes a numerical value determined by the fiber structure, mode and wavelength. This indicates that the bending loss of the fundamental mode of the communication wavelength and the higher-order mode of the test wavelength can be set independently.
The present invention uses this principle to perform cord contrast.

  First, the first feature of the present invention is a method of contrasting a single-mode optical fiber with reduced bending loss, wherein the wavelength of the test light is shorter than the effective cutoff wavelength of the fiber. It is a characteristic contrast control method. As described above, the wavelength of the test light is set to a wavelength shorter than the cutoff wavelength of the optical fiber used in the transmission line to be tested, thereby performing the core contrast using the bending loss of the higher order mode. It becomes possible.

  Further, in order to effectively perform the core line contrast, it is necessary to set the test wavelength to a wavelength having a reasonably large bending loss in the higher-order mode. Moderately large is the distance from the transmitter that enters the test light into the fiber to the receiver that detects the leaked light, and the higher-order mode propagates without being significantly attenuated by the bending applied to the normal line. This means that the bending loss is small to the extent that the bending loss is large to the extent that the higher-order mode leaks due to the bending loss by applying a bending diameter in a range normally assumed in the core wire contrast portion of the receiving unit. In general, if the bending loss of the higher-order mode at the test wavelength is 0.1 dB / turn or less at a bending diameter of 300 mmφ, the higher-order mode is applied to the normal line at the distance from the transmitter to the receiver. If the bending diameter is 5 mmφ and is 0.2 dB / turn or more, leakage light can be sufficiently detected by the receiving unit.

  FIG. 1 is a configuration diagram showing an embodiment of a core wire contrast device according to the present invention, in which reference numeral 1 is a transmission unit, 2 is a reception unit, 3 is a core wire control unit, 4 is an optical fiber cable, 5 is an optical transmission device, 6 is a closure, and 7 is an optical fiber. The optical fiber reference device of the present embodiment leaks by bending the transmitter 1 having a light source that makes test light incident on a specific optical fiber 7 and the desired position of the optical fiber 7 that has entered test light. The light source of the transmission part 1 is shorter than the cut-off wavelength of the optical fiber as described above. It is characterized by being set. A laser diode (LD) or the like is used as the light source of the transmission unit 1. A photodiode (PD) or the like is used as the light receiving element used in the receiving unit 2.

  The LP11 mode is desirable as the higher-order mode used for the contrast control. By using the LP11 mode, the wavelength difference between the test light and the communication light can be reduced. As a result, the test light can be set in the low loss wavelength band of the optical fiber made of quartz glass used in normal communication, and the distance from the transmission unit to the core wire reference unit of the reception unit can be further increased.

  It is desirable to set or design the wavelength of the light source of the transmission unit and the bending diameter of the core wire reference unit so that the bending loss of the LP11 mode is 0.1 dB / 180 ° or more. Since the core wire contrast device designed in such a manner generates a relatively large amount of leaked light, the detection mechanism of the core wire contrast portion can be configured at low cost, and the core wire contrast can be realized at low cost.

  The core wire contrast method of the present invention is particularly effective for measuring an optical fiber having a fundamental mode bending loss at a signal wavelength (use wavelength) of 0.1 dB / turn or less when it is wound once around a diameter of 30 mm. It is. This is because, even if the fiber cores are compared, it is very difficult or expensive to perform the core control by a known method because the bending loss in the fundamental mode is small and sufficient leakage light cannot be obtained. This is because a device is necessary.

  The wavelength of the test light is preferably in the range of 400 nm to 1260 nm. If it is 400 nm or less, loss such as Rayleigh scattering of quartz glass becomes large, and the distance between the transmitter and the receiver cannot be increased. If it is 1260 nm or more, the bending loss of the higher-order mode becomes large, and the communication wavelength band (0 band or the like) and the wavelength of the test light are undesirably covered. In particular, when LP11 mode bending loss is used for detection, it is desirable that the thickness be 600 nm to 1240 nm in consideration of LP11 mode bending loss. If it is 600 nm or less, the bending loss may be too small to detect leaked light. If it is 1240 nm or more, the bending loss of the higher-order mode is large, and the higher-order mode is at a distance from the transmitter to the core-line control part. May be greatly attenuated by bending applied to a normal line.

  In addition, if the wavelength of the test light is selected from any of the group consisting of 633 nm, 808 nm, 850 nm, 980 nm, and 1060 nm, an existing inexpensive light source can be used. The core contrast can be realized. It should be noted that the light source wavelength is a guideline, and in reality, fluctuation / expansion of about ± 20 nm is allowed due to wavelength broadening and manufacturing variations.

  Further, avoiding the wavelength of 850 nm used in short-range communication and setting the wavelength of the test light in the range of 860 nm to 1240 nm is desirable because 850 nm can be used for communication.

  The bending diameter applied to the core wire control part is preferably in the range of 5 mm to 60 mm. If the applied bending diameter is 5 mm or less, the bending may cause the fiber to break (or give damage to the fiber to be measured that will lead to a future break). On the other hand, if it is 60 mm or more, the size of the core wire contrast portion becomes large and the handling becomes inconvenient.

  Further, as is done in a known contrast control device, modulating the test light by an appropriate method can detect only the test light in synchronism with the modulation, so that a line including an amplifier is used. In addition, since it is possible to perform core line contrast even in a live line (a line on which communication is performed), this is a preferable application example.

[Prototype Example 1]
-Transmitter light source: LD
Wavelength: 978nm ± 20nm
Power: ≧ -5dBm
Modulation: 270 Hz / 1 kHz / 2 kHz / continuous light switching / receiving unit Light receiving element: PD (InGaAs)
Detectable light: 270 Hz / 1 kHz / 2 kHz / continuous light Receiving sensitivity: ≦ −40 dBm
Bending part of core wire contrast part: 5 to 60 mmφ bending application (head part is replaced and used in the above range)

  When a core wire contrast experiment was performed using this core wire contrast device, core wire contrast was possible in all the fibers described in Non-Patent Document 4. In addition, the bending part (head) with the optimal bending diameter is selected with respect to various fibers, and the core wire is contrasted thereon.

[Prototype example 2]
-Transmitter light source: LD
Wavelength: 633nm ± 20nm
Power: ≧ -5dBm
Modulation: 270 Hz / 1 kHz / 2 kHz / continuous light switching / receiving unit Light receiving element: PD (Si)
Detectable light: 270 Hz / 1 kHz / 2 kHz / continuous light Receiving sensitivity: ≦ −40 dBm
Bending part of core wire contrast part: 5 to 60 mmφ bending application (head part is replaced and used in the above range)

  When a core wire contrast experiment was performed using this core wire contrast device, core wire contrast was possible in all the fibers described in Non-Patent Document 4. In addition, the bending part (head) with the optimal bending diameter is selected with respect to various fibers, and the core wire is contrasted thereon.

[Prototype Example 3]
-Transmitter light source: LD
Wavelength: 1064nm ± 20nm
Power: ≧ -10dBm
Modulation: 270 Hz / 1 kHz / 2 kHz / continuous light switching / receiving unit Light receiving element: PD (InGaAs)
Detectable light: 270 Hz / 1 kHz / 2 kHz / continuous light Receiving sensitivity: ≦ −40 dBm
Bending part of core wire contrast part: 5 to 60 mmφ bending application (head part is replaced and used in the above range)

  When a core wire contrast experiment was performed using this core wire contrast device, core wire contrast was possible in all the fibers described in Non-Patent Document 4. In addition, the bending part (head) with the optimal bending diameter is selected with respect to various fibers, and the core wire is contrasted thereon.

[Prototype Example 4]
-Transmitter light source: LD
Wavelength: 808nm ± 20nm
Power: ≧ -5dBm
Modulation: 270 Hz / 1 kHz / 2 kHz / continuous light switching / receiving unit Light receiving element: PD (Si)
Detectable light: 270 Hz / 1 kHz / 2 kHz / continuous light Receiving sensitivity: ≦ −40 dBm
Bending part of core wire contrast part: 5 to 60 mmφ bending application (head part is replaced and used in the above range)

  When a core wire contrast experiment was performed using this core wire contrast device, core wire contrast was possible in all the fibers described in Non-Patent Document 4. In addition, the bending part (head) with the optimal bending diameter is selected with respect to various fibers, and the core wire is contrasted thereon.

[Prototype Example 5]
-Transmitter light source: LD
Wavelength: 915nm ± 20nm
Power: ≧ -5dBm
Modulation: 270 Hz / 1 kHz / 2 kHz / continuous light switching / receiving unit Light receiving element: PD (Si)
Detectable light: 270 Hz / 1 kHz / 2 kHz / continuous light Receiving sensitivity: ≦ −40 dBm
Bending part of core wire contrast part: 5 to 60 mmφ bending application (head part is replaced and used in the above range)

  When a core wire contrast experiment was performed using this core wire contrast device, core wire contrast was possible in all the fibers described in Non-Patent Document 4. In addition, the bending part (head) with the optimal bending diameter is selected with respect to various fibers, and the core wire is contrasted thereon.

It is a block diagram which shows one Embodiment of the core wire contrast apparatus which concerns on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Transmission part, 2 ... Reception part, 3 ... Core wire contrast part, 4 ... Optical fiber cable, 5 ... Optical transmission apparatus, 6 ... Closure, 7 ... Optical fiber core wire.

Claims (12)

  A method for contrasting single-mode optical fibers with reduced bending loss, wherein the test wavelength is shorter than the effective cutoff wavelength of the optical fiber.   2. The method according to claim 1, wherein the test wavelength is set to a wavelength at which a bending loss of a higher-order mode of the measured fiber is reasonably large.   The cord control method according to claim 2, wherein the higher order mode is an LP11 mode.   4. The method of contrasting core wires according to claim 3, wherein the bending diameter and wavelength of the core wire contrast portion are set so that the bending loss of the LP11 mode at the test wavelength is 0.1 dB / 180 ° or more.   The optical fiber whose bending loss of the fundamental mode at the signal wavelength is 0.1 dB / turn or less when it is wound once around a diameter of 30 mm is an object to be measured. Core wire contrast method.   The cord control method according to claim 2, wherein the test wavelength is selected from 400 nm to 1260 nm.   6. The method according to claim 4, wherein the test wavelength is selected from 600 nm to 1240 nm.   The cord test method according to claim 7, wherein the test wavelength is any one of 633 nm, 808 nm, 850 nm, 980 nm, and 1060 nm.   The cord test method according to claim 7, wherein the test wavelength is selected from 860 nm to 1240 nm.   The method of contrasting cores according to any one of claims 1 to 9, wherein a bending diameter of the core contrast part is in a range of 5 mm to 60 mm.   11. The method according to claim 1, wherein the test light is modulated, and the modulated signal is detected by a receiving unit.   A transmission unit having a light source for injecting test light into an optical fiber, a core line control unit for generating leakage light by bending a desired position of the optical fiber into which the test light is incident, and a light receiving element for detecting the leakage light A cord contrast device, comprising: a light source capable of performing the cord contrast method according to any one of claims 1 to 11; apparatus.

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