JP2006210975A - Method for measuring dynamic range of optical transmission line - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a matter that there is no method for measuring the dynamic range of an optical fiber transmission line quantitatively, and a method for measuring the sensitivity or dynamic range of optical transmission apparatus, e.g. a light emitting element, a light receiving element, a connector, a transmission line, and the like, being used in a television broadcast system and of the entire system using the optical apparatus quantitatively is needed. <P>SOLUTION: In an optical transmission line where a transmitting section having a light emitting element and a receiving section having a light receiving element are coupled through an optical fiber transmission line, the method for measuring the dynamic range of the optical fiber transmission line is arranged to measure attenuation of light propagating on the optical fiber transmission line by inserting at least one optical filter for attenuating the light propagating on the optical fiber transmission line by a predetermined amount into the optical fiber transmission line. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for measuring the dynamic range of an optical transmission line, and more particularly to a method for measuring the dynamic range of an optical transmission line for transmitting television images.

  A camera device for television broadcasting, a video production camera, or an industrial camera is used from a camera control device (generally referred to as a CCU: Camera Control Unit; hereinafter referred to as a CCU device) placed at a remote place. This is a camera control system that performs various controls (generally referred to as a camera head, hereinafter referred to as a camera head). There are various types of these camera control systems, but most of them perform adjustment of the field of view and imaging direction of the camera head installed in the remote place from the CCU device, or video adjustment and audio adjustment of the camera head. It is. The camera head and the CCU device are connected by a coaxial cable or the like, and power is supplied to the camera head. Recently, transmission of these various control signals and video signals has changed from analog signals to digital signals. Furthermore, the connection between the camera head and the CCU device has also changed from using a coaxial cable to using an optical cable (optical transmission line).

  Thus, in the television broadcasting and video production camera system, the length of the cable for connection between the camera head and the CCU device is 100 m to several hundreds m in the studio in the broadcasting station. In addition, the length is about 1 to 3 km in outdoor soccer relay or golf relay. In the case of an optical cable, the attenuation of light to be transmitted is generally extremely small, and its use is expanding because it is superior to a coaxial cable for long-distance transmission.

  However, when this optical cable is used for a long period of time, there are cases where desired transmission characteristics cannot be obtained due to secular change, dirt, a decrease in transmittance due to bending of the optical cable, defective connectors, and the like. And, in order to broadcast the video by appropriately switching the plurality of camera heads and the CCU device, a plurality of optical cables are used, but if it is connected to an optical cable with poor transmission characteristics, the video quality deteriorates, In the worst case, video may not be transmitted. As is well known, in public broadcasting such as television broadcasting and video production camera systems, there should be no accidents such as interruption of broadcast programs, and they can be stabilized stably for a long time under various environmental conditions. Great care is taken to maintain.

  FIG. 4 is a diagram showing a camera head and a CCU device used in a conventional television broadcasting system. In FIG. 4, 401 is a camera head that captures an image of an object, 402 is an optical fiber transmission path that transmits an image signal captured by the camera head 401, and 403 is a CCU device that controls the camera head 401. Reference numeral 404 denotes a light emitting element such as a semiconductor laser or an LED (Light Emitting Diode), which functions to convert an image signal captured by the camera head 401 into an optical signal. Reference numeral 405 denotes a connector portion that functions to efficiently couple the light emitted from the light emitting element 404 to the optical fiber transmission line 402. Since this connector part 405 is a connector well known from the past, detailed description is omitted. As the light receiving element 406, for example, a phototransistor, a photodiode, or the like is used. The light receiving element 406 converts an optical signal transmitted through the optical fiber transmission path 402 into an electrical signal and supplies the electrical signal to the CCU device 403. Reference numeral 407 denotes a connector portion that functions to efficiently couple light from the optical fiber transmission path 402 to the light receiving element 406. Since this connector portion 407 is also a well-known connector, a detailed description thereof will be omitted. The CCU device 403 appropriately processes an electrical signal from the light receiving element 406 and displays it on a monitor screen (not shown) or transmits an image signal to another transmission path.

  On the other hand, the CCU device 403 performs adjustment of the field of view and imaging direction of the camera head 401 installed in a remote place, or video adjustment and audio adjustment of the camera head, so that the control signal from the CCU device 403 is transmitted through an optical fiber. It is transmitted to the camera head 401 via the path 402. In this case, the light emitting element is provided on the CCU device 403 side and the light receiving element is provided on the camera head 401 side, which is a so-called bidirectional transmission structure, but is not directly related to the present invention. In FIG. 4, the description is omitted.

  Thus, in the conventional television broadcasting system shown in FIG. 4, when the transmission efficiency of the optical fiber transmission path 402 is deteriorated, a transmission failure occurs in the transmission of the signal between the camera head 401 and the CCU 403. In the case of signal transmission, transmission of an image signal may stop suddenly, which is fatal in public television broadcasting. The reasons why the transmission efficiency of the optical fiber transmission line 402 is deteriorated include an increase in attenuation due to contamination of the optical fiber transmission line, a defect in the connector, a decrease in transmittance due to bending of the optical fiber transmission line, and the aging of the optical fiber transmission line. Changes are possible.

  Therefore, in the conventional television broadcasting system shown in FIG. 4, before starting broadcasting, for example, the light emitting element 404 and the optical fiber transmission line 402 are removed at the connector unit 405, and the amount of light emitted by the light emitting element 404 is set to, for example, , Measured by a light quantity measuring device, then, the light emitting element 404 and the optical fiber transmission path 402 are coupled, the optical fiber transmission path 402 and the light receiving element 406 are removed at the connector portion 407, and the light quantity from the optical fiber transmission path 402 is, for example, Measure with a light meter. If the measurement result is equal to or greater than the predetermined light amount, the television broadcast system has been determined to operate normally.

  Such a conventional method cannot quantitatively measure the dynamic range of the optical fiber transmission line, and can also be used for optical transmission equipment such as a light emitting element, a light receiving element, a connector, a transmission line, and the like used in a television broadcasting system. There are problems such as the inability to quantitatively measure the sensitivity and dynamic range of the entire system in which equipment is used, as well as the quantitative measurement in the operating state of the television broadcasting system. A new optical transmission line to solve these problems. Realization of a dynamic range measurement method is desired.

Not particularly found.

  An object of the present invention is to provide a method for measuring the dynamic range of an optical transmission line that can quantitatively measure the dynamic range of the optical fiber transmission line.

  Another object of the present invention is to provide a method for measuring the dynamic range of an optical transmission line capable of quantitatively measuring the sensitivity and dynamic range of the optical transmission equipment such as the transmission line and the entire system using the optical equipment. .

  Another object of the present invention is to provide a method for measuring the dynamic range of an optical transmission line that enables quantitative measurement in the operating state of a television broadcasting system.

  Still another object of the present invention is to provide a method for measuring the dynamic range of an optical transmission line that can predict the deterioration of a television broadcasting system and the possibility of extending an optical fiber transmission line.

  The method for measuring a dynamic range of an optical transmission line according to the present invention includes: an optical transmission line in which a transmission unit having a light emitting element and a reception unit having a light receiving element are coupled via an optical fiber transmission line; At least one attenuation optical filter for attenuating the light transmitted through the path by a predetermined amount is inserted, and the attenuation of the light transmitted through the optical fiber transmission path is measured.

  Further, in the method for measuring a dynamic range of an optical transmission line according to the present invention, when the attenuation optical filter is inserted into the optical fiber transmission line and the attenuation amount of light transmitted through the optical fiber transmission line is measured, the predetermined amount is attenuated. Each time the attenuation optical filter is increased by one, the attenuation amount of the light transmitted through the optical fiber transmission line is measured.

  Also, in the dynamic range measurement method for an optical transmission line according to the present invention, a criterion for determining the suitability of attenuation is set for the attenuation of light transmitted through the optical fiber transmission line, and one attenuation optical filter for attenuating the predetermined amount is provided one by one. The optical fiber transmission line attenuation amount obtained each time the optical fiber transmission line is increased is compared with the suitability judgment criterion, and the suitability judgment of the optical transmission line is made based on the comparison result.

  In the method for measuring a dynamic range of an optical transmission line according to the present invention, the attenuation optical filter includes an attenuation optical filter selected from attenuation optical filters having different predetermined attenuation amounts.

  As described above, according to the present invention, it is possible to quantitatively measure the dynamic range of an optical fiber transmission line, and to quantify the sensitivity and dynamic range of an optical transmission device such as a transmission line and the entire system using the optical device. Measurement is possible. In addition, since quantitative measurement can be performed in the operating state of the television broadcast system, excellent effects such as prediction of deterioration of the television broadcast system and possibility of extension of the optical fiber transmission line can be expected.

  Embodiments according to the present invention will be described below with reference to the drawings. FIG. 1 is a diagram for explaining a schematic configuration of an embodiment of the present invention. In FIG. 1, reference numerals 101-1, 101-2,... 101-5 denote attenuation optical filters, respectively. These attenuation optical filters are provided between the optical fiber transmission lines 102 and 103, and function to attenuate the transmittance of light passing through the optical fiber transmission lines 102 and 103 by a predetermined amount. For example, the attenuation optical filters 101-1, 101-2,... 101-5 shown in FIG. 1 (referred to as the attenuation optical filter 101 when the attenuation optical filter is generically referred to) are respectively light. When transmitting through the attenuating optical filter, the transmitted light is attenuated by 2 dB. Therefore, when five attenuating optical filters 101 are used, the transmitted light is attenuated by about 10 dB in total. In this embodiment, an example in which one attenuation optical filter 101 is 2 dB will be described. However, one attenuation optical filter 101 may be one that attenuates 5 dB or one that attenuates 10 dB. Needless to say, it is necessary to appropriately change the system configuration and the measurement target.

  Reference numerals 104 and 105 denote connectors for connecting the attenuation optical filter 101 to predetermined portions of the optical fiber transmission path 402 via the optical fiber transmission paths 102 and 103. Reference numeral 106 denotes an attenuation measuring device, and 107 denotes a display device such as a monitor. In addition, the same code | symbol is attached | subjected to the same thing as FIG. The attenuation measuring device 106 measures the attenuation by detecting, for example, a change in the amount of light incident on the light receiving element 406 as a change in current. Further, in the display device 107, for example, deterioration of the transmission signal can be visually observed by displaying a color bar signal or a resolution chart for inspecting the resolution of the TV signal. It is also possible to determine the deterioration of the transmission signal. In the above embodiment, transmission between the camera head 401 and the CCU device 403 has been described. Generally, a transmission unit having a light emitting element and a receiving unit having a light receiving element are connected to an optical fiber transmission line. The present invention can be applied to an optical transmission line that is coupled via a cable.

  In FIG. 1, the optical fiber transmission line 402 is displayed short, but in reality, as described above, the length of the cable for connection between the camera head and the CCU device is small for a studio in a broadcasting station. It can be 100m to several hundred meters. In addition, the length is about 1 to 3 km in outdoor soccer relay or golf relay. On the other hand, the length between the connectors 104 and 105 including the attenuation optical filter 101 shown in FIG. 1 is about 1 m. The attenuation optical filter 101, the optical fiber transmission lines 102 and 103, and the connectors 104 and 105 are referred to as an optical filter 108 for measurement. Further, in the embodiment shown in FIG. 1, the optical filter 108 for this measurement has been described with respect to the measurement of attenuation for one-way transmission of signals from the camera head 401 to the CCU device 403. As described above, Since a signal such as a control signal is transmitted from the CCU device 403 to the camera head 401, the optical filter 108 for measurement is configured to be provided in both directions, that is, two configured by two parallel lines. Therefore, an optical filter 108 for measuring the above is provided.

  Next, the operation of the present invention will be described. First, the system of the present invention has the same configuration as the conventional television broadcasting system shown in FIG. 4, but a predetermined portion of the optical fiber transmission line 402 is separated before starting the broadcasting of this television broadcasting system. It is assumed that an optical filter 108 for measurement is attached. Therefore, the system of the present invention has a structure in which a predetermined portion of the optical fiber transmission line 402 of the conventional television broadcasting system is coupled by a connector, and for example, one side of the connector 104 and one side of the connector 105 are connected. By separating this connector, as shown in FIG. 1, an optical filter 108 for measurement can be connected. FIG. 1 shows this state. For example, when the quantitative measurement of the dynamic range of the optical fiber transmission line is completed, the optical filter 108 for measurement is removed, and one side of the connector 104 and one side of the connector 105 are connected to each other. It is configured and operated as a broadcasting system.

  FIG. 2 is a diagram showing transmission characteristics of the entire television broadcasting system shown in FIG. In FIG. 2, the vertical axis represents the transmittance (dB) of the entire television broadcasting system including the optical fiber transmission path 402, and the horizontal axis represents time. This transmission characteristic can be measured by the attenuation measuring device 106, for example. For example, a transmittance of 0 dB (corresponding to an attenuation of 0 dB) indicates that an output signal (for example, a predetermined rated output signal) of the camera head 401 is transmitted to the 100% CCU device side. When the transmittance is −10 dB or less (attenuation amount is 10 dB or more), the transmission signal is greatly deteriorated, and the output signal of the camera head 401 is not transmitted to the CCU device side, so that it does not operate well as a so-called television broadcasting system. Represents. The transmission characteristics shown in FIG. 2 are merely examples, and needless to say, the transmission characteristics need to be experimentally determined in advance in consideration of the system configuration, environment, and other broadcast content specialities.

  Here, in FIG. 1, as the light emitting element 404 to be used, the wavelength λc of the emitted light is 1266 nm to 1360 nm, for example, and the average output P is, for example, −10 dB to −3 dB. . Hereinafter, a method for measuring the transmittance (attenuation rate) of this embodiment will be described.

  First, when the optical filter 108 for measurement is inserted into the optical fiber transmission line 402, the optical filter 108 for measurement having one attenuation optical filter 101-1 is inserted, and the entire television broadcasting system is operated. The transmission rate of the transmission signal is measured by the attenuation measuring device 106. That is, the attenuation from the average output P of the light emitting element is measured. In this case, it is assumed that the attenuation is 2 dB (transmittance -2 dB). Next, an optical filter for measurement 108 including two optical filters for attenuation 101-1 and 101-2 is inserted to operate the entire television broadcasting system, and the attenuation measuring device 106 attenuates the transmission signal. Measure the amount. In this case, it is assumed that the attenuation is 4 dB (transmittance −4 dB). When the attenuation optical filters 101 are increased one by one in this way and the attenuation is measured sequentially, the result shown in FIG. 3 is obtained.

  In FIG. 3, the number of stages indicates the number of attenuation optical filters 101 inserted into the optical filter 108 for measurement. The attenuation amount indicates the attenuation amount (corresponding to the transmittance) measured by the attenuation measuring device 106. Appropriateness indicates the result of determining whether or not the television broadcasting system operates satisfactorily with the attenuation amount measured by the attenuation amount measuring device 106. That is, when the attenuation amount of the optical transmission line or the optical transmission system is equal to or greater than a predetermined value (or the transmittance is equal to or less than the predetermined value), the attenuation amount at which the operation is not normal is determined as a threshold value in advance through experiments or the like. to decide. For example, in the number of stages 3, the attenuation is 6 dB, and in the attenuation of 10 dB or more as a television broadcasting system, there is still a margin of 4 dB until the limit value that does not work well. It shows that it works well as a broadcasting system. That is, it shows that there is a margin in the dynamic range of the optical fiber transmission line. However, when the number of stages is 4, the attenuation factor is 8 dB, and the dynamic range of the optical fiber transmission line has no margin, indicating that this attenuation factor does not work well as a television broadcast system, and is suitable for use as a television broadcast system. I understand that there is no. Therefore, in the present embodiment, the threshold value for the attenuation amount of the suitability determination is 6 dB (−6 dB in terms of transmittance).

  Therefore, it is possible to quantitatively know whether there is a margin in the dynamic range of the optical fiber transmission line of the television broadcasting system measured from the measurement result shown in FIG. For example, in the case of the present embodiment, as a result of measuring the attenuation measuring device 106 by inserting the optical filter 108 for measurement including the three optical filters 101 for attenuation, the attenuation amount is 6 dB, and still reaches 10 dB. It can be seen that there is still a sufficient margin until the deterioration of the transmission characteristics, such that there is a margin of 4 dB. Therefore, for example, the use of the optical fiber transmission path 402 can be further extended to perform outdoor television relaying. Note that the suitability determination based on the number of stages, the amount of attenuation, and the threshold shown in FIG. 3 is not limited to this, and may be determined experimentally in consideration of the configuration, scale, image quality, etc. of the television broadcasting system. .

  On the other hand, the transmission characteristics of the television broadcasting system have already greatly deteriorated, and the attenuation measuring device 106 is measured by inserting an optical filter 108 for measurement including one (one) attenuation optical filter 101. In such a case, if the attenuation amount is already 10 dB from the average output P of the light emitting element, it means that the dynamic range has only 2 dB margin and the television broadcasting system does not operate stably. Therefore, in this case, it is possible to take measures such as replacing the optical fiber transmission path 402 with a new one. Thus, excellent effects such as prediction of deterioration of the television broadcasting system and possibility of extension of the optical fiber transmission line can be expected.

  Although the present invention has been described in detail above, the present invention is not limited to the embodiments of the dynamic range measurement method of the optical transmission line described herein, and the dynamic range measurement method of the optical transmission line other than those described above. Needless to say, it can be widely applied to.

It is a figure which shows schematic structure of one Example of this invention. It is a figure which shows the characteristic curve for demonstrating operation | movement of this invention. It is a figure for demonstrating operation | movement of this invention. It is a figure which shows an example of the conventional television broadcast system.

Explanation of symbols

  101: optical filter for attenuation, 102, 103, 402: optical fiber transmission line, 104, 105, 405, 407: connector, 106: attenuation measurement device, 107: display device, 108: optical filter for measurement, 401: Camera head, 403: CCU, 404: light emitting element, 406: light receiving element.

Claims (3)

  Attenuating light for attenuating a predetermined amount of light transmitted through the optical fiber transmission line to the optical fiber transmission line in an optical transmission line in which a transmission unit having a light emitting element and a receiving unit having a light receiving element are coupled via an optical fiber transmission line A method for measuring a dynamic range of an optical transmission line, comprising: inserting at least one filter; and measuring an attenuation amount of light transmitted through the optical fiber transmission line.   2. The method for measuring a dynamic range of an optical transmission line according to claim 1, wherein when the attenuation optical filter is inserted into the optical fiber transmission line and the attenuation of light transmitted through the optical fiber transmission line is measured, the predetermined amount is attenuated. A method for measuring a dynamic range of an optical transmission line, comprising: measuring an attenuation amount of light transmitted through the optical fiber transmission line each time the attenuation optical filter is increased by one.   3. The method for measuring a dynamic range of an optical transmission line according to claim 2, wherein a criterion for determining whether or not the attenuation is appropriate is set for the attenuation of the light transmitted through the optical fiber transmission line, and the attenuation optical filters for attenuating the predetermined amount one by one. A method for measuring the dynamic range of an optical transmission line, comprising: comparing the attenuation amount of the optical fiber transmission line obtained each time the optical fiber transmission line is obtained with the criteria for determining suitability; and determining the suitability of the optical transmission line based on a comparison result. .

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