JP2002300113A - Optical space transmission system and optical transmitter and optical receiver, and optical transmitter-receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical space transmission system that can prevent deterioration in the communication quality even under exposure by the sun ray or under a bad weather so as to improve the reliability and to provide an optical transmitter, an optical receiver and an optical transmitter-receiver. SOLUTION: In the optical space transmission system comprising the optical transmitter 1 with a communication light transmission means 11 transmitting a communication light and the optical receiver 3 with a communication light receiving means 31 receiving the communication light transmitted through space, the optical receiver 3 is provided with a background light detection means 32 that detects the intensity of the background light around the communication optical reception terminal 35, a luminous quantity revision means 33 that revises the luminous quantity received by the communication light receiving means 31, and a background light intensity transmission means 34 that transmits the background light intensity detected by the background light detection means 32 to the optical transmitter 1, and the optical transmitter 1 is provided with a background light intensity reception means 12 that receives the background light intensity sent form optical receiver 3 and an output revision means 13 that revises the optical transmission output of the communication light transmission means 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical space transmission system, an optical transmitter, an optical receiver, and an optical transmitter / receiver, and more particularly, to an optical transmitter and an optical receiver installed separately from each other. The present invention relates to an optical space transmission system capable of transmitting and receiving communication light through space.

[0002]

2. Description of the Related Art Hitherto, a so-called optical space transmission system has been known in which signals such as video, audio, and data are converted into laser light or LED light and space is communicated with light. This system includes an optical transmitting device that converts a transmission signal into light and transmits the light, and an optical receiving device that receives a light beam emitted from the optical transmitting device at a distance of several meters to several kilometers. Although there are models of this device that can communicate not only analog signals but also digital signals, unlike radio radio devices, they can handle signals with a very wide band,
In addition, despite no need for a communication license, it is not as widely used as radio wave radio communication devices. There is also a so-called SS radio, which uses spread spectrum, for radio wave radio communication, a communication means that does not require a user's license. In the case of radio wave radio communication, unlike the light beam of optical communication, Since the emission spreads over a wide range, it is easily assumed that when the number of users increases, the receiving device receives many radio waves and interferes with each other, thereby making it impossible to receive. On the other hand, in the case of optical communication, it is a system that directly receives a narrow beam within a viewable range, so that interference can be sufficiently avoided unless intentionally disturbed by aiming at the optical receiving device, It seems very promising for future communication systems.

However, the following factors can be cited as factors that greatly hinder the spread of the optical space transmission. The first factor is that the weather greatly affects communication quality. The second factor is the difficulty in aligning a light beam used for transmission. The third factor is a problem of security against laser light and LED light used for communication.

[0004] The first factor will be described in more detail. The effects of the weather are, in part, the effects of sunlight in fine weather,
Another is the effect of rain, snow, fog, etc. in bad weather. Usually, this optical space transmission device is generally used outdoors in most cases, but sunlight in fine weather gives the device the following interference. The relationship between the spectra of sunlight is shown in FIG. 17 (source: Laser Fundamentals, Optronics). The wavelength of laser light and LED light used for optical space transmission is generally around 800 nm in the infrared. As can be seen from FIG. 17, a very high wavelength of solar energy is used. The light receiving element such as a photodiode used for the communication light receiving means of the optical space transmission device is naturally set with a high sensitivity to the wavelength of the light around 800 nm, and the light receiving element is saturated when irradiated with sunlight. It is often reported that communication is lost. As a countermeasure, a hood or an optical filter that blocks sunlight is used. However, the angle at which the sunlight is irradiated varies widely over the course of one day and even throughout the year. It is difficult. Also,
Solar energy is 10% of the communication light used for optical space transmission.
Since it has energy more than 00 times, it is also hindered by the reflected light of sunlight, so even if an optical filter is used, the light energy near 800 nm of sunlight is strong, so the effect cannot be expected so much. It is in. Next, although interference is caused by rain, snow, and fog, the light beam used for communication is scattered by these water droplets, and the communication quality is degraded. The attenuation due to bad weather in the optical space transmission is shown in FIG. 18 (Source: Optical Space Transmission Network Technical Data, Optronics). Especially in the case of fog and dense fog, the disturbance is very large and communication is almost impossible.

Next, the second factor will be described in detail. As mentioned earlier, laser light and LED light are used in the space optical transmission device. However, light is scattered when space transmission is performed over a communication distance of several tens of meters to several kilometers. Is not capable of optical transmission. Here is why laser light with low scattering is used for optical communication,
On the contrary, there arises a problem that the light beam cannot be accurately applied to the optical receiver. For example, the diameter of a light beam that can be received at a point several kilometers away is about several tens to several hundred meters even if the amount of communication light is maximized, and the angle is only several degrees or less. The weight of the conventional optical space transmission device can be as high as several tens of kilograms including the rain cover when installed outdoors, and it takes a great deal of labor to accurately transmit the light to the optical receiver. I need. It is also very difficult to hold this in the correct position. If the mounting method is bad, it often happens that the irradiation angle of the communication light is significantly deviated due to its own weight over time.

[0006] Regarding the safety of the third factor, laser light causes a great deal of damage to the retina and the skin of the eyes as recently reported on televisions and newspapers, many examples of accidents involving retinal damage caused by a laser pointer. Likely to give. LED
Light is treated almost the same as laser light internationally, IEC60825 internationally, and JIS C domestically.
6082 specifies the handling method in detail. In the case of an optical space transmission system, in particular, in order to eliminate the first and second disturbances, a laser beam or an LED used for optical communication is used.
Increasing the light output increases the effect, but may also result in a loss of security. When increasing the output of optical communication, it is necessary to give consideration to safety as well.

FIG. 14 shows a general external view of a conventional optical space transmission device 4 '. There are many models composed of a pair of optical transmitting means 41 'and optical receiving means 42'. This is a device intended for two-way communication of data, etc., the same device is used for the other party, and this optical transmission signal is received by the optical receiving means of the other party, and conversely, the optical transmission signal of the other party is The signal is received by this optical receiving means. In the case of communication in only one direction, such as video, some models have separate optical transmission means and optical reception means.

[0008] In the conventional optical space transmission apparatus, FIG.
As shown in the figure, a light emitting element 15 'such as a laser diode
Is emitted into space by an optical lens 18 'as a beam as nearly parallel as possible. The diameter of the optical lens 18 'of the light transmitting means is about 50 mm. On the other hand, the light receiving means has a large light receiving window in order to secure as much light receiving amount as possible, and as shown in FIG.
The light is condensed on a light receiving element 36 'such as a photodiode via a light receiving lens 38'. The diameter of the light receiving lens 38 'of the light receiving means may be 100 mm or more in order to make light collection efficient, but if the aperture is widened, the light receiving lens 38' is easily affected by sunlight. There is also a model in which an optical filter is attached to the light receiving window for the purpose of reducing the influence of sunlight, but as shown in FIG. 17, light having a high solar energy component of around 800 nm is used as the wavelength of communication light. Therefore, if sunlight is attenuated by the optical filter, the communication light is also attenuated, and the effect of the optical filter cannot be expected.

[0009]

SUMMARY OF THE INVENTION The present invention solves the problems of the prior art, and is useful in situations where there is a lot of background light, such as exposure to sunlight, or in adverse weather, where communication light decreases. Another object of the present invention is to provide an optical space transmission system, an optical transmitting device, an optical receiving device, and an optical transmitting and receiving device capable of preventing deterioration of communication quality and ensuring communication quality.

[0010]

SUMMARY OF THE INVENTION The present invention provides a communication light transmitting terminal for transmitting communication light, an optical transmission device having communication light transmitting means, a communication light receiving terminal for receiving communication light for transmitting space, and a communication light. In an optical space transmission system including an optical receiving device including a receiving unit, the optical receiving device is input to a background light intensity detecting unit that detects an intensity of background light around a communication light receiving terminal, and is input to the communication light receiving unit. Light amount changing means for changing the light amount, and background light intensity transmitting means for transmitting the background light intensity detected by the background light intensity detecting means to the light transmitting device, and the light transmitting device is transmitted from the light receiving device. An optical space transmission system includes a background light intensity receiving unit that receives background light intensity, and an output changing unit that changes an optical transmission output of the communication light transmitting unit.

Further, according to the present invention, when the background light intensity is equal to or higher than a predetermined upper limit value, the output changing means of the light transmitting device increases the light transmission output, and the light receiving device has the light amount changing means of the communication light. This is an optical space transmission system that reduces the amount of light input to the receiving means. It goes without saying that when the background light intensity returns to the state where it does not exceed the upper limit, the light transmission output is returned to the original level.

Thus, background light (mainly sunlight) having a nearby light wavelength used for communication light is detected, and when the intensity of the background light is large (the background light intensity is equal to or more than a predetermined upper limit), communication is performed. Increasing the transmission output of the light transmitting means, and reducing the ratio of background light by reducing the overall light reception amount by the mechanical light amount changing means provided in the light receiving device, thereby reducing the ratio of the background light. Communication quality can be ensured. The background light intensity detecting means for detecting the strong background light can be realized by, for example, a light measuring means using a photodiode. Then, the situation in which the background light is strong is fed back to the optical transmission device to increase the light transmission output, thereby increasing the ratio of the amount of communication light to the background light. On the other hand, in the communication light receiving means, if this state is left as it is, the amount of input light is large, and the light receiving element is saturated, so that accurate information cannot be obtained. Therefore, in the communication light receiving means, a light amount changing means (such as an optical filter for attenuating light) is inserted before the light receiving element to reduce the total amount of light input to a state where the light receiving element is not saturated, so that information can be accurately obtained. To be obtained. The light amount changing means has means for continuously changing and switching the amount of light passing therethrough according to the intensity of the background light. For example, the light amount changing means uses an optical filter capable of continuously changing the amount of attenuation of the light. It can be realized by means such as automatically determining the amount of light passing therethrough according to the intensity of light.

According to the present invention, when the background light intensity is equal to or lower than a predetermined lower limit, the output changing means of the light transmitting device increases the light transmission output, while the light receiving device has the light amount changing means of the communication light. This is an optical space transmission system in which the amount of light input to the receiving means is set to a maximum value or a certain value or more.

In a state where the amount of communication light input to the communication light receiving means cannot be sufficiently ensured due to bad weather such as rain, snow, fog, etc., the light output of the communication light transmitting means is increased, and The light quantity changing means adjusts the light quantity of the communication light input to the communication light receiving means so as to be a maximum value or a certain value or more. In the case of bad weather, the level of the background light input to the background light intensity detecting means of the optical receiver becomes low. Therefore, when the amount of the background light is below a certain level (below a predetermined lower limit), it is determined that the weather is bad. The optical filter of the light amount changing means is set to zero or replaced with a very small one, and in this situation, this information is transmitted to the background light intensity of the light transmitting device by using the background light intensity transmitting means in the light receiving device. Feedback is provided to the receiving means, and the optical transmission output is increased to a level at which information from the optical transmitter is sufficiently transmitted, thereby ensuring communication quality. Since the information fed back from the optical receiving device to the optical transmitting device is at the level of the brightness of the background light (mainly sunlight), it can be adequately dealt with by a general public network or a self optical communication channel. In addition, in the night of fine weather, since there is no background light (mainly sunlight), the background light intensity detecting means determines that the background light intensity is low.
Although this is the same condition as bad weather, communication light is sufficiently secured during the night when the weather is fine, which is the optimal condition for optical communication. In such a case, the background light intensity transmission means in the optical receiver is used. If the information of the communication light is fed back to the optical transmission device to reduce the optical transmission output, the optical filter of the light amount changing means is no problem even if it is zero or slight as in the case of bad weather. There is no. The point is that in fine weather, the signal level required for optical transmission of communication light is increased so as not to lose to the background light to increase the S portion in the S / N ratio. This indicates that communication quality is ensured. The above method makes it possible to greatly reduce the influence of the weather, and the effect is enormous. The background light intensity detection means can be easily realized by a normal photodiode, and since the amount of information for feeding back this to the optical transmitter is small,
It can be easily realized using a general public network or a self-optical communication path.

Further, the present invention is the optical space transmission system, wherein the optical transmission device has an optical fiber as a means for outputting communication light from a light emitting element provided in the communication light transmitting means to space.

As shown in FIG. 4, the communication light from the light emitting element 15 is condensed by, for example, a lens and guided by an optical fiber 16, and then, for example, this light is irradiated on a parabolic antenna and transmitted. it can. Since the light of the light emitting element 15 of the communication light transmitting means is transmitted to the space via the optical fiber 16, the communication light transmitting terminal is replaced with the optical light transmitting device instead of the light transmitting device having several kilograms to several tens of kilograms conventionally. It is also possible to reduce the number of communication optical transmitting terminals that actually perform transmission to 1 kilogram or less. This has the advantage that installation outdoors is greatly simplified compared to the prior art. If an optical fiber is used, this terminal can be used without a power source.
In a conventional apparatus, a power supply is required as a matter of course. For outdoor use, it is necessary to consider not only the safety of the laser beam but also the safety of the power supply. In the present invention, an optical fiber is used, and a communication light transmitting terminal that outputs light is outdoors and has no power supply, while an optical transmission device main body including a light emitting element and communication light transmitting means is disposed indoors safely. This makes it possible to significantly improve the safety of the power supply and the reliability of the device as compared with the case where the optical transmission device main body is installed outdoors. In addition, when the optical fiber comes off from a predetermined position due to dropping or the like, it is naturally necessary to take measures such as turning off the power of the communication light transmitting means and stopping the light transmission in order to ensure safety.

Further, the present invention is the optical space transmission system, wherein the optical transmission device has an output changing means for changing the amount of communication light input from the light emitting element of the communication light transmitting means to the optical fiber.

When the communication light is guided by the optical fiber from the light emitting element of the communication light transmitting means, for example, when the light is input from the laser diode to the optical fiber, the light transmission of the laser diode can be changed by a relatively easy means. Changing the output can be realized.

According to the present invention, the optical transmitting apparatus has a plurality of communication light transmitting means and a number output adjusting means for adjusting the optical transmission output of the communication light according to the number of used communication light transmitting means. This is an optical space transmission system.

By using a plurality of communication light transmitting means, it can be used for increasing communication light in fine weather or increasing communication light in bad weather. The output of the communication light of the optical transmission device can be increased, and, for example, as shown in FIG. 5, three identical communication light transmitting units 11a to 11c are prepared,
The number of the communication light transmitting means 11 is increased or decreased according to the information on the background light obtained by the background light intensity detecting means of the light receiving device. When the communication state is good, one is transmitted, and when the communication state is very bad, three pieces are transmitted. It is possible to secure the amount of information necessary for optical communication by switching the number of uses, such as using all. Switching of the number to be used is easy either manually or automatically. Also, by providing a number output adjusting means for adjusting the optical transmission output of the communication light according to the number of the communication light transmitting means 11 used, the information amount necessary for the optical communication can be more appropriately secured.

Further, according to the present invention, in the optical transmission apparatus, the optical transmission device may further include: a spectroscopic unit configured to separate communication light from a light emitting element provided in the communication light transmission unit; This is an optical space transmission system having a transmission terminal.

The communication light from the light emitting element provided in the communication light transmitting means is split by a light separating means such as an optical coupler, so that the communication light can be substituted for a plurality of communication light transmitting means. As shown in FIG. 6, for example, the communication light transmitting terminals 14a to 14a to
If three communication terminals 14c are installed and used, even if one communication optical transmission terminal 14 interferes with transmission due to an accident or the like, communication is possible, and optical path disturbances such as birds are dealt with. it can. Having many light emitting elements such as laser diodes requires measures such as preventing laser light from leaking to the outside as stipulated in JIS, and requires a great deal of expense for safety management. . Branching and transmitting the communication light from a single light emitting element has great advantages in terms of increased security and cost. The light from a light emitting element such as a laser diode provided in the communication light transmitting means is split and each light is used as one communication light transmitting terminal. In this case, it is not necessary to prepare a plurality of the same communication light transmitting means, and the second light source for optical communication can be easily produced.

Further, the present invention is the above-mentioned optical transmission apparatus, which is an optical space transmission system having a plurality of optical fibers for separating light from a light emitting element provided in a communication light transmitting means.

When dispersing the communication light from one light emitting element 15, as shown in FIG. 7, it is possible to disperse the communication light into a plurality of optical fibers 16a to 16c using an optical coupler or the like. By doing so, the terminals of the optical fiber 16 become the input and output ends of light, a plurality of output ends of light can be easily obtained, and a plurality of outputs of the communication light transmitting means can be produced by simple means. You can do it.

Further, the present invention is the optical space transmission system, wherein the optical receiving device has an optical fiber for guiding received communication light to a light receiving element of communication light receiving means.

As shown in FIG. 8, the light receiving portion of the communication light receiving terminal is formed by an optical fiber 38 and guided to the light receiving element 36 via the optical fiber 38. Terminals can also be significantly smaller and lighter. Further, the optical fiber can be used without a power supply, and the safety of the power supply can be sufficiently improved.

[0027] Further, the present invention is the optical space transmission system, wherein the optical receiving apparatus has a plurality of optical fibers for guiding communication light received by a communication light receiving terminal to a light receiving element of communication light receiving means.

When light is collected from a parabolic antenna or a concave mirror and sent to a communication light receiving means via an optical fiber for processing, as shown in FIG.
The light received by .about.38c can be collected by the light receiving element 36 to perform signal processing. This advantage is simpler than in the past, in that, for example, even if one optical fiber 38 is damaged or suffers an optical path obstruction, communication quality can be ensured by another optical fiber 38. It is in.

Further, according to the present invention, in the above optical transmission device, the wavelength of the communication light used for transmission is set to an optical space having a wavelength equal to or less than 1/4 of the optical energy having a wavelength of 800 nm in the sunlight spectrum. It is a transmission system.

By using a wavelength of communication light used for transmission that is less affected by sunlight, it is possible to improve communication quality in fine weather. As shown in the conventional example,
Laser light or LE near 800nm with high solar energy
The use of D light is disadvantageous because it is affected by sunlight in fine weather. If the wavelength is around 1400 nm, sunlight is also greatly attenuated, which is less than one-fourth that of light near 800 nm, and the communication quality of communication light is greatly improved. Also, since longer wavelengths are more resistant to interference, 1400
A wavelength near nm is more suitable for communication light.

According to the present invention, the optical receiving apparatus includes an optical band-pass filter that mainly transmits light near a wavelength of communication light among optical signals input to a light receiving element provided in communication light receiving means. Optical transmission system having

The optical receiver has an optical band-pass filter that mainly passes light near the wavelength of the communication light, and the ratio of the communication light contained in the optical signal input to the light receiving element of the communication light receiving means. Can be increased. Since a photodiode generally used as a light receiving element has a considerably wide sensitivity to a wavelength to be received, as shown in FIG. The diode immediately saturates, making optical communication impossible. Therefore, even if communication light of a wavelength having a relatively low energy in the sunlight spectrum is selected, the influence of sunlight remains. As a solution to this, an optical bandpass filter is inserted in front of a light-receiving element such as a photodiode so that communication light having a wavelength necessary for optical communication is input more than sunlight. The influence of light is minimized, and communication quality can be ensured.

Further, the present invention is an optical space transmission system, wherein the communication light transmitting terminal of the optical transmitting device or the communication light receiving terminal of the optical receiving device has a parabolic antenna or a concave mirror.

The communication light transmitting terminal and the communication light receiving terminal are shown in FIG.
As shown in FIG. 0 and FIG. 11, parabolic antennas 17 and 37 or a concave mirror similar thereto are used as terminals for transmitting or receiving communication light. Thus, the parabolic antenna 1
When the 7 or concave mirror is used as a communication light transmitting terminal, there is an effect of avoiding concentration of laser light or LED light used for communication light per unit area, and even if the light is radiated to eyes or skin, it is unlikely to cause an obstacle. . At the same time, a wide light beam can be ensured for the communication light, which is effective in preventing light path interference by birds and the like. For example, in the case of a thin light beam, it is often reported that the light path is obstructed by birds such as sparrows and crows. This problem can be easily solved with a wide light source. 2. Description of the Related Art A conventional optical space transmission apparatus transmits laser light or LED light to a space through a lens having a diameter of about 5 cm. As described above, since the laser beam or the LED light has a high risk of causing damage to eyes and skin when the beam is small, it is necessary to produce a light beam as wide as possible so as to reduce the intensity per unit area. However, if the diameter of the lens is to be made larger than it is now, the cost of the lens itself is considerably increased, and it is difficult to realize the lens. By irradiating the light emitting element 15 to the parabolic antenna 17 or a concave mirror as shown in FIG.
Light rays having a width of m to several meters can be produced, and the light density per unit area can be reduced, which can greatly contribute to safety. Conversely, if the light density per unit area is the same as the conventional one, the amount of communication light to be applied can be increased and the communication quality can be significantly increased. If this is used for a communication optical receiving terminal as shown in FIG. 11, a significantly larger light receiving area can be secured as compared with the conventional optical space transmission apparatus. A large lens in the conventional optical space transmission apparatus is very expensive in terms of price, but the parabolic antenna 37 has an advantage that a relatively large area can be easily secured. As shown in FIG. 11, light hitting the parabolic antenna 37 or the concave mirror is collected and collected by the light receiving element 36. Therefore, in the case of the parabolic antenna, it is possible to collect light tens to hundreds of times in area in comparison with the conventional lens.

Further, according to the present invention, the optical transmitting apparatus or the optical receiving apparatus is an optical transmitting / receiving apparatus including a communication optical transmitting terminal and a communication optical transmitting unit, and a communication optical receiving terminal and a communication optical receiving unit. This is an optical space transmission system that transmits and receives light using the same parabolic antenna or concave mirror.

As shown in FIG. 12, transmission and reception of communication light
This is performed using the parabolic antennas 43. At the focal point of the parabolic antenna 43, the light emitting element or the tip of the optical fiber 41 guided from the light emitting element and the light receiving element or the tip of the optical fiber 42 leading to the light receiving element are installed. Generally, many optical space transmission apparatuses perform bidirectional communication.
Therefore, as shown in FIG. 14, the optical transmitter and the optical receiver are provided in the same housing. Although the light transmitting means and the light receiving means are separated from each other, by performing this with one parabolic antenna 43, it is possible to present a direction different from the conventional direction. Near the focal point of the parabolic antenna 43, the terminal of the transmitting optical fiber 41 and the receiving optical fiber 42
It can be realized by placing a terminal. This makes it possible to use the same parabolic antenna 43 for both transmission and reception of communication light, which contributes to cost reduction. In this case, of course, the wavelength of the light for transmission and the wavelength of the light for reception use different wavelengths as in the past, and the optical receiving device is provided with the communication light transmitted from the light emitting element so as not to interfere with the reception. It is necessary to insert an optical filter and the like. Further, in terms of price, it will further contribute to a significant price reduction, and the effect can be expected to be enormous which is not available in the conventional method.

According to the present invention, the optical transmission apparatus is an optical space transmission system comprising: a spreader for spectrum-spreading a digital signal; and an optical converter for converting the spectrum-spread signal into an optical signal.

Processing gain is obtained by spreading the spectrum at the final stage. As a result, the communication quality can be significantly improved, and the communication quality can be ensured under bad conditions such as rain, snow, and fog. In a conventional optical transmission device, means for directly converting an analog or digital signal into light and transmitting the signal is used. In bad weather, it is very difficult to ensure communication quality due to the above-mentioned effects of rain, snow, fog, and the like. However, in the event of a disaster, it is necessary to ensure communication quality in order to accurately grasp the disaster situation. According to the present invention, this communication quality is ensured by using spread spectrum. Instead of optically converting a digital signal as it is, the digital signal is optically converted once after being spread. When the spread spectrum is used in this way, as shown by Shannon's theorem, the SN ratio is improved by the spread, and the spread processing gain can be improved. FIG. 13A is a block diagram of the present invention. Conventionally, the input signal is directly converted into light by means such as FM modulation or digitally converted and then converted into light and transmitted spatially. However, in the present invention, the spread spectrum 22 is inserted after the digital conversion 21. And E
/ O (electrical / optical) conversion 24. Spread spectrum is an effective means for accurately capturing information even when the SN ratio is in a poor state, and is known to be a means capable of improving the SN ratio by the processing gain. Therefore, this method significantly improves the effect of sunlight in fine weather and the attenuation of light due to water droplets such as rain, snow, and fog in bad weather.

Further, the present invention is the optical space transmission system, wherein the optical transmitting apparatus has a selecting means for converting a digital signal into an optical signal or converting a spectrum-spread signal into an optical signal.

When the spread spectrum 22 is performed, the baseband signal must be spread at a high speed in order to obtain a spread gain, and the operation speed is limited. As a result, it is not suitable for high speed communication. As described above, factors that deteriorate the communication quality are the effects of rain, snow, and fog in bad weather and the effects of background light (mainly sunlight) in fine weather, as shown in FIG. Under the condition of deteriorating the communication quality, the signal subjected to spread spectrum 22 is selected by the changeover switch 23. On the contrary, in a situation where high communication quality can be ensured, the digital conversion is performed without performing the spread spectrum 22. The selected signal is selected by the changeover switch 23 and subjected to E / O conversion 24. In this way, for example, even in an emergency due to bad weather such as storm and flood damage, it is possible to secure communication means by the spread spectrum 22, and the effect is very large. The changeover of the changeover switch 23 can be detected automatically by the above-described background light intensity detection means and can be automatically changed, or can be manually changed manually.

Further, according to the present invention, there is provided the above-mentioned optical transmission apparatus, wherein the optical spatial transmission means includes an automatic alignment means for changing the transmission angle of the communication light to be transmitted when the center of the communication light received by the optical reception apparatus is shifted. System.

If the center of the communication light received by the optical receiver is left shifted, the communication light may not be able to be received. Therefore, the center of the received communication light is shifted by a predetermined distance or more. Then, the optical receiving apparatus instructs the optical transmitting apparatus to change the transmission angle of the communication light. As the instruction means, for example, the background light intensity transmitting means and the background light intensity receiving means are used.

The present invention also provides a communication light transmitting terminal for transmitting communication light and an optical transmission device including communication light transmitting means, wherein the background light intensity receiving means for receiving the background light intensity transmitted from the light receiving device; An output changing means for changing an optical transmission output of the communication light transmitting means.

According to the present invention, there is provided a communication light receiving terminal for receiving communication light transmitted from an optical transmitting device and an optical receiving device provided with communication light receiving means, wherein the intensity of background light around the communication light receiving terminal is detected. Background light intensity detection means
A light amount changing unit for changing the light amount of the optical signal input to the communication light receiving unit; and a background light intensity transmitting unit for transmitting the background light intensity detected by the background light intensity detecting unit to the optical transmitting device. is there.

Further, the present invention relates to an optical transmission / reception device comprising a communication light receiving terminal for transmitting communication light and receiving communication light transmitted from a communication partner, and communication light transmitting / receiving means. The means has a parabolic main body composed of a parabolic surface or a concave mirror main body composed of a concave mirror for emitting and receiving an optical signal, a radiation optical fiber for emitting light, and an input optical fiber for inputting light. One of the ends of the radiation and input optical fibers is an optical transmitting / receiving device provided near the focal point of the parabolic surface.

[0046]

Embodiments of the present invention will be described. Embodiments of an optical space transmission system, an optical transmitter, an optical receiver, and an optical transceiver according to the present invention will be described with reference to FIGS. FIG. 1 is an explanatory diagram of an optical space transmission system according to an embodiment. FIG. 2 is an explanatory diagram of the optical transmission device according to the embodiment. FIG. 3 is an explanatory diagram of the optical receiving device in the embodiment.

An embodiment will be described. As shown in FIG. 1, the optical free space transmission system of the present embodiment
And the optical receiving device 3. As shown in FIG. 2, the optical transmission device 1 includes a communication light transmission unit 11, a background light intensity reception unit 1,
2. It comprises an output changing means 13 and a communication light transmitting terminal 14. Note that the communication light transmitting terminal 14 may be included in the communication light transmitting means 11 in some cases. The communication light transmitting terminal 14 sends out the communication light obtained by converting the input signal to the optical receiver 3. The background light intensity receiving means 12 receives the background light intensity transmitted from the light receiving device 3. The output changing means 13 changes the light transmission output of the communication light transmitting means 11 according to the background light intensity received by the background light intensity receiving means 12. The output of the communication light transmitting means 11 is transmitted to the optical receiving device 3 via the communication light transmitting terminal 14. As shown in FIG. 3, the light receiving device 3 includes a communication light receiving unit 31, a background light intensity detecting unit 32,
A light amount changing unit 33, a background light intensity transmitting unit 34, and a communication light receiving terminal 35 are provided. The communication light receiving terminal 35 directly receives the communication light from the optical transmission device 1. Communication light receiving means 3
Reference numeral 1 includes a light receiving element and the like, and receives communication light from the optical transmission device 1 via the communication light receiving terminal 35. At that time, part or all of the background light (mainly sunlight) is also input. The background light intensity detecting means 32 has a light receiving element such as a photodiode, for example, and detects the intensity of the background light around the communication light receiving terminal 35. The background light intensity detection means 32 detects the intensity of sunlight in fine weather, rain,
You can know bad weather such as snow and fog. Light intensity changing means 3
Reference numeral 3 denotes, for example, an optical filter, and a communication light receiving unit 31.
To change the amount of light of the optical signal input to. The background light intensity transmitting means 34 is a means for transmitting the intensity of the background light to the optical transmitting device 1. For example, the background light intensity detected by the background light intensity detecting means 32 is transmitted using a general public network or a self-optical communication path. Transmit to the transmitting device 1. The optical transmitter 1 varies the output of the communication light based on the information on the background light intensity.

In the optical space transmission system of this embodiment,
The background light intensity detecting means 32 of the light receiving device 3 detects the intensity of background light such as sunlight around the communication light receiving terminal 35, and the light amount changing means 33 sends the communication light receiving means 31 to the communication light receiving means 31 based on the background light intensity. Change the light amount of the optical signal. The background light intensity transmitting means 34 transmits the background light intensity to the optical transmitter 1. In the light transmitting device 1, the background light intensity receiving means 12 receives the background light intensity from the light receiving device 3, and the output changing means 13 changes the light transmission output of the communication light transmitting means 11 based on the background light intensity. Since the communication light near 800 nm is easily affected by the background light (mainly sunlight) as described above, it is more advantageous to use the wavelength near 1400 nm, which is hardly affected by the background light, as the communication light.

In the embodiment, when the background light intensity around the communication light receiving terminal 35 is equal to or higher than a predetermined upper limit value such as when the weather is fine,
The light amount changing means 33 of the light receiving device 3
Reduce the amount of light to one. On the other hand, the output changing unit 13 of the optical transmitting device 1 increases the optical transmission output of the communication optical transmitting unit 11. As a result, the input can be reduced on the receiving side (both S and N in the S / N ratio can be reduced) to avoid a saturation state in the light receiving element, and the communication light component (S) can be increased on the transmitting side. It is possible to obtain an optical space transmission system that can ensure the space and increase the reliability.

In the embodiment, when the background light intensity around the communication light receiving terminal 35 is lower than a predetermined lower limit value such as bad weather,
The output changing means 13 of the optical transmission device 1
1 increases the optical transmission output. On the other hand, contrary to the fine weather, the light amount changing means 33 of the light receiving device 3
To a maximum value or a certain value or more. As a result, even in a state where the amount of communication light received by the optical receiving device 3 is reduced due to bad weather, communication quality can be ensured by increasing the output on the transmission side, and an optical space transmission system with increased reliability is obtained. be able to.

[0051]

According to the present invention, there is provided an optical space transmission system capable of preventing a decrease in communication quality and ensuring communication quality even in a situation where the apparatus is exposed to sunlight or in bad weather. Obtainable.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an optical space transmission system according to an embodiment.

FIG. 2 is an explanatory diagram of an optical transmission device according to an embodiment.

FIG. 3 is an explanatory diagram of an optical receiving device in an embodiment.

FIG. 4 is an explanatory diagram of Example 1 of the optical transmission device according to the present invention.

FIG. 5 is an explanatory diagram of Example 2 of the optical transmission device according to the present invention.

FIG. 6 is an explanatory diagram of Example 3 of the optical transmission device according to the present invention.

FIG. 7 is an explanatory diagram of Example 4 of the optical transmission device according to the present invention.

FIG. 8 is an explanatory diagram of Example 1 of the optical receiver according to the present invention.

FIG. 9 is an explanatory diagram of Example 2 of the optical receiver according to the present invention.

FIG. 10 is an explanatory diagram of Example 5 of the optical transmission device according to the present invention.

FIG. 11 is an explanatory diagram of Example 3 of the optical receiver according to the present invention.

FIG. 12 is an explanatory diagram of an example of an optical transceiver according to the present invention.

FIG. 13 is an explanatory diagram of Example 6 of the optical transmission device according to the present invention.

FIG. 14 is an explanatory diagram of an optical space transmission apparatus according to the related art.

FIG. 15 is an explanatory diagram of an optical transmission device in a conventional technique.

FIG. 16 is an explanatory diagram of an optical receiver according to a conventional technique.

FIG. 17 is an explanatory diagram of a solar spectrum.

FIG. 18 is an explanatory diagram of weather conditions and attenuation of near-infrared rays.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical transmission device 11 Communication light transmission means 12 Background light intensity reception means 13 Output change means 14 Communication light transmission terminal 15 Light emitting element 16 Optical fiber 17 Parabolic antenna 21 Digital conversion 22 Spectrum spread 23 Switching switch 24 E / O conversion 3 Light reception Device 31 Communication light receiving means 32 Background light intensity detecting means 33 Light intensity changing means 34 Background light intensity transmitting means 35 Communication light receiving terminal 36 Light receiving element 37 Parabolic antenna 38 Optical fiber 4 Optical transmitting / receiving device 41 Light emitting element 42 Light receiving element 43 Parabolic antenna 4 'Optical space transmission device 41' Optical transmitting means 42 'Optical receiving means 15' Light emitting element 18 'Optical lens 36' Light receiving element 38 'Light receiving lens

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04B 10/06 10/04 // H03G 3/32 (72) Inventor Tomomi Kishi 6 Nishigotanda, Shinagawa-ku, Tokyo −25−11 F-term in Fujiya Electric Works (reference) 5J100 JA08 SA01 SA02 5K002 BA02 CA02 CA08 CA09 DA05 FA03 5K060 BB08 CC06 LL01

Claims (39)

[Claims] An optical transmission device including a communication light transmitting terminal for transmitting communication light and communication light transmitting means, a communication light receiving terminal for receiving communication light for transmitting space, and an optical receiving device including communication light receiving means. In the optical space transmission system comprising: the light receiving device, a background light intensity detecting means for detecting the intensity of the background light around the communication light receiving terminal, and a light amount changing means for changing the light amount input to the communication light receiving means, Background light intensity transmitting means for transmitting the background light intensity detected by the background light intensity detecting means to the optical transmitting device, and the light transmitting device receives the background light intensity transmitted from the optical receiving device. An optical space transmission system comprising: an intensity receiving unit; and an output changing unit that changes an optical transmission output of the communication optical transmitting unit. 2. When the background light intensity is equal to or higher than a predetermined upper limit, the output changing means increases the light transmission output of the optical transmitting apparatus, and the light receiving means has the light amount changing means input to the communication light receiving means. The optical space transmission system according to claim 1, wherein the amount of light to be transmitted is reduced. 3. When the background light intensity is equal to or less than a predetermined lower limit, the output changing means increases the light transmission output of the light transmitting apparatus, while the light receiving means changes the light amount input to the communication light receiving means. 2. The optical space transmission system according to claim 1, wherein the amount of light is set to a maximum value or a fixed value or more. 4. The optical space transmission system according to claim 1, wherein the optical transmission device has an optical fiber as a means for outputting communication light from a light emitting element provided in the communication light transmitting means to a space. 5. The free-space optical transmission system according to claim 4, wherein the optical transmission device has an output changing unit that changes the amount of communication light transmitted from the light emitting element of the communication light transmitting unit to the optical fiber. 6. The optical transmission apparatus according to claim 1, further comprising a plurality of communication light transmitting means, and a number output adjusting means for adjusting the optical transmission output of the communication light according to the number of used communication light transmitting means. Optical space transmission system. 7. The optical transmission device according to claim 1, further comprising: a spectroscopic unit that splits the communication light from the light emitting element provided in the communication light transmitting unit into a plurality of light beams, and separates the separated communication light into independent optical transmission outputs. The optical space transmission system according to claim 6, wherein 8. The free-space optical transmission system according to claim 7, wherein said optical transmission device has a plurality of optical fibers for separating communication light from a light emitting element of a communication light transmitting means. 9. The optical free space transmission system according to claim 1, wherein said optical receiving device has one or more optical fibers for guiding received communication light to a light receiving element of communication light receiving means. 10. The optical transmission apparatus according to claim 1, wherein the wavelength of the optical signal used for transmission is set to a wavelength of 80% of the light spectrum of sunlight.
2. The optical space transmission system according to claim 1, wherein the wavelength has a light energy of 1/4 or less of the light energy of 0 nm. 11. The free-space optical transmission system according to claim 1, wherein the optical receiving device has an optical bandpass filter that passes light near a wavelength of an optical signal used for transmission. 12. The optical space transmission system according to claim 1, wherein the communication light transmitting terminal of the light transmitting device or the communication light receiving terminal of the light receiving device has a parabolic antenna or a concave mirror. 13. The optical transmitting device or the optical receiving device for transmitting communication light is an optical transmitting and receiving device including a communication light transmitting terminal and a communication light receiving terminal, and performs transmission and reception on the same parabolic antenna or concave mirror. 2. The optical space transmission system according to claim 1, wherein 14. The optical space transmission system according to claim 1, wherein the optical transmission device includes a spreader for spectrum-spreading the digital signal, and a means for electrical / optical conversion of the spectrum-spread signal into an optical signal. 15. The optical transmitter according to claim 1, further comprising a selector for converting a digital signal into an optical signal or converting a spectrum-spread signal into an optical signal.
5. The optical space transmission system according to 4. 16. The optical free space transmission system according to claim 1, wherein the communication light transmitting terminal or the communication light receiving terminal is constituted by a combination of an optical fiber and a parabolic antenna or a concave mirror, so that no power is supplied. 17. The optical space transmission according to claim 1, further comprising feedback means for varying information light transmitted from the optical transmission device by transmitting information of the background light and communication light from the optical reception device to the optical transmission device. system. 18. The optical space transmission system according to claim 17, wherein the light amount changing means provided in the light receiving device changes the amount of light passing therethrough based on information of the background light. 19. The optical space according to claim 1, wherein the optical transmission device includes an automatic alignment unit that changes a transmission angle of the communication light to be transmitted when the center of the communication light received by the optical reception device is shifted. Transmission system. 20. An optical transmitter comprising a communication light transmitting terminal for transmitting communication light for transmitting space and a communication light transmitting means, comprising: a background light intensity receiving means for receiving background light intensity transmitted from the light receiving apparatus; An optical transmission device comprising: an output changing unit that changes an optical transmission output of the communication optical transmitting unit. 21. The optical transmission device according to claim 20, wherein the output changing means increases the optical transmission output when the background light intensity around the communication light receiving terminal is equal to or higher than the upper limit or equal to or lower than the lower limit. 22. The optical transmission apparatus according to claim 20, further comprising an optical fiber as a means for outputting communication light from a light emitting element provided in the communication light transmitting means to a space. 23. The optical transmitting apparatus according to claim 20, further comprising an output changing means for changing an amount of communication light transmitted from the light emitting element provided to the communication light transmitting means to the optical fiber. 24. A communication apparatus comprising: a plurality of communication light transmitting means; and a number output adjusting means for adjusting an optical transmission output of communication light according to the number of the communication light transmitting means used.
The optical transmission device as described in the above. 25. A splitting means for splitting communication light from a light-emitting element provided in the communication light transmitting means into a plurality of light beams, and each of the split communication light beams as an independent optical transmission output.
5. The optical transmission device according to 4. 26. The optical transmitting apparatus according to claim 25, further comprising a plurality of optical fibers for separating communication light from a light emitting element provided in said communication light transmitting means. 27. The wavelength of an optical signal used for transmission is a wavelength having a light energy of 1/4 or less of a light energy of a wavelength of 800 nm in a solar spectrum.
The optical transmission device as described in the above. 28. The optical transmission device according to claim 20, wherein the communication optical transmission terminal has a parabolic antenna or a concave mirror. 29. The optical transmission apparatus according to claim 20, further comprising: a spreader for spectrum-spreading the digital signal; and an optical converter for converting the spectrum-spread signal into an optical signal. 30. The optical transmitting apparatus according to claim 29, further comprising a selecting unit for converting a digital signal into an optical signal or converting a spectrum-spread signal into an optical signal. 31. The optical transmitting apparatus according to claim 20, wherein the communication optical transmitting terminal is constituted by a combination of an optical fiber and a parabolic antenna or a concave mirror so that no power is supplied. 32. An optical receiving device comprising a communication light receiving terminal for receiving communication light for transmitting space and a communication light receiving means, comprising: a background light intensity detecting means for detecting an intensity of background light around the communication light receiving terminal; A light amount changing means for changing a light amount inputted to the communication light receiving means, and a background light intensity transmitting means for transmitting the background light intensity detected by the background light intensity detecting means to the light transmitting device. Receiver. 33. The optical receiver according to claim 32, further comprising one or more optical fibers for guiding the received communication light to a light receiving element provided in the communication light receiving means. 34. The optical receiving apparatus according to claim 32, further comprising an optical bandpass filter that allows light near the wavelength of communication light to pass through said optical receiving apparatus. 35. The optical receiving device according to claim 32, wherein the communication optical receiving terminal has a parabolic antenna or a concave mirror. 36. The optical receiving apparatus according to claim 32, wherein when the background light intensity is equal to or greater than a predetermined upper limit, the optical receiving apparatus reduces the amount of light input to the communication light receiving means by the light amount changing means. 37. When the background light intensity is equal to or less than a predetermined lower limit, the light receiving device sets the light amount input to the communication light receiving unit to a maximum value or to a certain value or more. The optical receiver according to any one of the preceding claims. 38. The optical receiving device according to claim 32, wherein the communication optical receiving terminal is constituted by a combination of an optical fiber and a parabolic antenna or a concave mirror so that no power is supplied. 39. An optical transmission / reception terminal comprising a communication light transmitting / receiving terminal for transmitting communication light and receiving communication light transmitted through a space, and a communication light transmitting / receiving device, wherein the communication light directly receives and transmits the communication light. Optical transmitting and receiving terminals
A parabolic main body composed of a parabolic surface for receiving and reflecting light or a concave mirror main body composed of a concave mirror, a radiation optical fiber for emitting light, and an input optical fiber for inputting light, and An optical transmission / reception device, wherein one of the ends of the input and output optical fibers is provided near the parabolic surface or near the focal point of the concave mirror, respectively.