WO2018193750A1

WO2018193750A1 - Video conferencing system

Info

Publication number: WO2018193750A1
Application number: PCT/JP2018/009302
Authority: WO
Inventors: 並木　周; 松浦　裕之
Original assignee: 国立研究開発法人産業技術総合研究所
Priority date: 2017-04-18
Filing date: 2018-03-09
Publication date: 2018-10-25

Abstract

Provided is a video conferencing service with which flexible connections are possible and which allows for a strong sense of presence between a plurality of sites via an optical path network using signal processing and a comparatively simple structure. In this video conferencing system, a video camera provided at each site captures video. The electrical signal of each captured video is transmitted to a conversion station after having been converted into light at an optical transmitter. When doing so, the wavelength of the optical signal from each of the video cameras is made to differ, and if there is a plurality of video cameras in each site, the optical signals are subjected to wavelength multiplexing. The optical signals from the sites are combined in the conversion station and then distributed, whereby copies of the combined optical signals are transmitted to the sites. From among the optical signals that have been transmitted from the conversion station, the optical signal that should be displayed at each site is selected by a wavelength selector and then converted by an optical receiver into an electrical signal that can be displayed by a display. A plurality of displays is provided at each site so as to surround a meeting participant, for example, and a display corresponding to the video from the other sites is displayed on the displays.

Description

Video conferencing system

The present invention relates generally to a video conference system, and more specifically to a video conference system via an optical path network that connects a plurality of points bi-directionally with optical fibers.

In recent years, a system called a video conference or a video conference in which voice and an image are transmitted between a plurality of distant points is widely spread. In a conventional video conference system, moving image captured by a video camera and audio data collected by a microphone are taken into the system. The captured data is converted into IP (Internet Protocol) data using a data compression technique, and then transmitted to a remote location using an Internet line. At the remote site, the transmitted IP data is converted into a signal that can be received by a display or speaker. By doing this in both directions, a video conference over an IP network between remote locations is realized.

In such a video conference, in order to increase the presence, it is desired that the image has high definition and that the transmission delay of the image and sound is small. However, since the video conference system via the conventional IP network uses the data compression technique, it takes time for the calculation processing of the compression and decompression. In particular, transfer of high-definition moving image data with an enormous amount of data tends to cause a transfer delay. Therefore, there is an increasing demand for sharing large-capacity information such as high-definition video on the network with low delay.

As a technology that answers the demand, for example, there is a dynamic optical path network (Dynamic Optical Path Network (DOPN)) that connects a plurality of points with an optical switch using an optical switch as disclosed in Non-Patent Document 1. Reference 1 discloses an application to a video conference using an uncompressed 4K high-definition moving image as an example by using a DOPN configuration that uses optical transmission that establishes a path between any of the eight nodes when necessary. As a result, for example, ultra-high-definition video can be shared in real time between any remote locations without being compressed, enabling a video conferencing service with a higher sense of presence than a video conferencing system via a conventional IP network. .

The DOPN of Non-Patent Document 1 is effective in that ultra-high definition video can be shared in real time between any remote locations without being compressed. However, for example, after each captured image is converted into an Ethernet (registered trademark) signal using a computer (PC) together with a 4K video camera at each node, an optical signal that can further transmit the Ethernet (registered trademark) signal over a long distance with a transponder The structure and control are likely to be complicated.

As another conventional technique, as shown in the video wall system of FIG. 1, in order to realize a bidirectional connection between points, a full mesh, that is, an optical fiber is laid independently between all points. Yes. However, this method requires a large number of optical fibers, which is costly. Therefore, as an extension of the prior art, in other words, it is conceivable to reduce the number of optical fibers by using a wavelength division multiplexing (WDM) technology based on the conventional concept of the technology. For example, as shown in FIG. 2, the outputs of three cameras (A1, A2, A3) at point A are converted into optical signals of different wavelengths, wavelength-multiplexed by an optical multiplexer 30, and then sent to an exchange 31. The same applies to the three cameras at other points B, C, and D. In the switching station 31, the wavelength division multiplexed signal is divided by the optical demultiplexer 32, combined with the signal at another point by the optical multiplexer 33, amplified by the optical amplifier 34, and transmitted to each point as the wavelength multiplexed signal. At each point, a necessary optical signal is demultiplexed by the optical demultiplexer 35 and displayed on a display through a filter for wavelength selection.

In the method of FIG. 2, not only the number of parts is large, but the connection is fixed. In particular, it is not possible to meet demands such as connecting between points only one-to-one, connecting between four points, or realizing a plurality of separate connections simultaneously. In addition, if all the signals are sent to the receiving side and only the optical filter selection function on the receiving side is selected, the optical filter is intentionally operated at a point where it is not desired to connect, or the equivalent is performed. This makes it possible to wiretap video communication. In order to make the connection flexible without losing security such as eavesdropping, there is a configuration called WXC (Wavelength Cross 利用 Connect) using a wavelength selective switch (WSS: Wavelength Selective Switch) for the optical multiplexer 33 of the exchange 31. Necessary. In general, WSS is an expensive element part, and it is not easy to increase the number of WSS ports when the number of connection points increases.

The present invention improves the above-described problems of the conventional technology, and provides a video conference system capable of providing a video conference service with a high sense of presence between a plurality of points by a relatively simple configuration and signal processing via an optical path network. The purpose is to provide. Specifically, for example, a flexible connection such as realizing a video conference connection between a plurality of points with a small number of parts, or performing the connection only between selected points without fixing the connection. The goal is to achieve this without using expensive elements such as WSS.

As one aspect of the present invention, there is provided a video conference system that uses an optical path network that connects a plurality of points in two directions with an optical fiber via at least one exchange. The video conference system is configured such that at each point, (a) a plurality of video cameras, (b) a plurality of displays, and (c) moving image signals from the plurality of video cameras are assigned to each video camera. An optical transmitter for converting into an optical signal of a wavelength; and (d) an optical signal having a different wavelength from the optical transmitter is combined and output to the switching center via an optical fiber as a first wavelength multiplexed signal. A first optical multiplexer; and (e) demultiplexing a second wavelength multiplexed signal including an optical signal transmitted from an exchange station via an optical fiber from a point other than the point into optical signals having different wavelengths. A first optical demultiplexer for output, and (f) a first optical receiver for converting each of the optical signals from the first wavelength selector into a driving signal for displaying a moving image on a corresponding display. A machine. Further, the switching center includes (g) a third optical multiplexer that multiplexes each of the first wavelength multiplexed signals transmitted from each point and outputs the multiplexed signal as a third wavelength multiplexed signal; and (h) a third optical multiplexer. An optical demultiplexer that outputs the third wavelength multiplexed signal from the optical multiplexer to each of the optical fibers connected to each point; and (i) the first wavelength multiplexed signal sent from each point. To the selected point, the input of the first wavelength multiplexed signal to the third optical multiplexer is switched, and the third to the optical fiber connected to each point from the optical demultiplexer. And an optical matrix switch for switching the output of the wavelength multiplexed signal.

The outline of the operation using the video conference system of one embodiment of the present invention is as follows. (I) A moving image (for example, a high-definition moving image) is captured by the video camera at each point. (Ii) An electrical signal (moving image signal) having captured video information is directly converted into light by an optical transmitter (without IP conversion or image compression by a PC) and then transmitted to an exchange. . At this time, the wavelength of the optical signal is different for each video camera. If there are a plurality of video cameras at each point, the optical signal is wavelength-multiplexed. (Iii) The switching center transmits a combined optical signal copy to each point by distributing after combining the optical signal from each point. (Iv) At each point, an optical signal to be displayed is selected from the optical signals sent from the switching center by a wavelength selector (for example, an optical bandpass filter), and then displayed by an optical receiver (for example, a high definition). It is converted into an electrical signal (drive signal) that can be displayed on the display. (V) At each point, for example, a plurality of displays are installed so as to surround the conference participants, and moving images from other points are displayed on the corresponding display.

It is a figure which shows the example of a connection by the full mesh between the conventional 4 points | pieces. It is a figure which shows the example of a connection between 4 points | pieces using the conventional wavelength division multiplexing (WDM) technique. 1 is a diagram illustrating an overall configuration of a video conference system according to an embodiment of the present invention. It is a figure for demonstrating the operation | movement in the switching center of FIG. It is a figure for demonstrating the operation | movement in the switching center of FIG. It is a figure which shows the whole structure of the video conference system of other one Embodiment of this invention. It is a figure which shows the partial structure of the video conference system of one Embodiment of this invention. It is a figure which shows the partial structure of the video conference system of one Embodiment of this invention. It is a figure which shows the partial structure of the video conference system of one Embodiment of this invention. It is a figure which shows the partial structure of the video conference system of one Embodiment of this invention. It is a figure which shows the example of a connection between 4 points | pieces using the video conference system of one Embodiment of this invention.

Embodiments of the video conference system of the present invention will be described with reference to the drawings. In the following embodiments, the case where the number of connection points N = 4 (points A to D) is mainly described. However, the number N of points can be any number of 3 or more. In order to reduce the equipment and operating costs of the optical path network, a different wavelength is assigned to each video camera at each connection point, and light of the assigned wavelength is transmitted from the transmitter / receiver installed at each connection point. Allow signals to be transmitted / received. This makes it possible to apply wavelength division multiplex communication (WDM: Wavelength: Division: Multiplex) to the transmission path (optical path) between each connection point and the switching center, thereby reducing the number of optical fiber cores used. it can.

<First Embodiment>
FIG. 3 is a diagram showing the overall configuration of the video conference system according to the embodiment of the present invention. In FIG. 3, in the video conference system 100, an exchange 10 and four points 1 to 4 (A to D) are connected via

optical fibers

20 and 21. As the

optical fibers

20 and 21, for example, one two-core optical fiber can be used. The switching center 10 includes a controller 11, an optical coupler 16, an optical demultiplexer 18, an optical amplifier 12, and an optical matrix switch 14. The controller 11 performs control and maintenance of each device in the exchange. In FIG. 3, the signal line is omitted because it is complicated, but in reality, a signal line exists between the controller 11 and each device.

The optical matrix switch 14 in the switching center 10 has eight input ports (IN) 1 to 8 and eight output ports (OUT) 1 to 8. In the configuration example of FIG. 3, the optical matrix switch 14 has a connection relationship between the input port and the output port shown in FIG. In this case, connect the optical matrix switch 14 to IN5 → OUT1
IN6 → OUT2
IN7 → OUT3
IN8 → OUT4
Thus, the optical signals λ _A , λ _B , λ _C , and λ _D from each point can be connected to the input of the optical multiplexer (Coupler) 16. Furthermore, the connection of the optical matrix switch 14 is changed from IN1 to OUT5.
IN2 → OUT6
IN3 → OUT7
IN4 → OUT8
Thus, the wavelength multiplexed signals λ _{A to D} of the optical demultiplexer 18 after passing through the optical amplifier 12 can be sent to each point. In this way, the wavelength multiplexed signals transmitted from the points 1 to 4 through the optical fiber 20 are input to the four input ports (IN) 5 to 8 of the optical matrix switch 14, and the output port (OUT) 1 is switched by the switch operation. ˜4 to the optical coupler (Coupler) 16. The optical coupler (Coupler) 16 further multiplexes each of the wavelength multiplexed signals transmitted from each point, and outputs the optical signals as wavelength multiplexed signals λ _{A to D} including 12 different wavelengths λ _A1 to λ _D3 in FIG. Output to the amplifier 12.

The optical coupler 16 can be an optical coupler, that is, a power combiner, or an AWG (Arrayed Waveguide Grating) that is a wavelength multiplexer. The optical amplifier 12 amplifies the wavelength multiplexed signals λ _{A to D} as necessary. This is to compensate for the optical power loss lost due to factors such as the optical coupler (Coupler) 16, the next-stage optical demultiplexer (Distributor) 18, or the transmission distance. When the optical power loss is small, it is not necessary to amplify by the optical amplifier 12. In other words, the optical amplifier 12 is not an essential device. An optical demultiplexer 18 sends copies of the wavelength multiplexed signals λ _{A to D} sent via the optical amplifier 12 to the four input ports (IN) 1 to 4 of the optical matrix switch 14. The copies of the wavelength multiplexed signals λ _{A to D} are output from the output ports (OUT) 5 to 8 to each of the optical fibers 21 connected to each point by the switching operation of the optical matrix switch 14.

Each of the points A to D includes a controller 25, three video cameras 5, three displays 6, an optical demultiplexer 23, an optical transmitter T, and an optical receiver. R and a wavelength selector F are installed. A controller 25 controls each device. In FIG. 3, the signal line is omitted because it is complicated, but in reality, a signal line exists between the controller 25 and each device. The video camera 5 is used to transmit a moving image including a conference participant 7 (one or more people) toward another point. The three video cameras 5 are arranged so as to surround the front view of the conference participant 7. It is desirable that the video camera 5 and the display 6 have a high definition, for example, a 4K compatible device, and the number of frames per second can correspond to 60 frames or more.

The three displays 6 are arranged so as to surround the front view of the conference participant 7. For example, among the three displays 6 in front of the person 7 at the point A, the high-definition video of the person 7 at the point B is displayed on the left display, and the high-definition video of the person 7 at the point C is displayed on the center display. Is displayed, and the high-definition moving image of the person 7 at the point D is displayed without delay on the right display. As a result, an environment full of realism can be realized as if the person 7 at the point A is facing the same place as each person 7 at the other point. The same applies to other points.

The optical transmitter T at each point converts the moving image signal from each video camera 5 into an optical signal and outputs the optical signal to an optical multiplexer (Coupler) 23. At this time, the wavelength of the optical signal is set to be different for each transmitter corresponding to each video camera 5. For example, at point A, the wavelength sent to point B is λ _A1 , the wavelength sent to point C is λ _A2 , and the wavelength sent to point D is λ _A3 (λ _A1 ≠ λ _A2 , λ _A1 ≠ λ _A3 , λ _A2 ≠ λ _A3 ). Since these optical signals have different wavelengths, they can be wavelength-multiplexed by an optical coupler (Coupler) 23 such as an optical coupler. For wavelength multiplexing, an AWG (Arrayed Waveguide Grating) or the like can be used instead of an optical coupler. In FIG. 3, the light wavelengths λ _A1 , λ _B1 , λ _C1 , λ _D1 , λ _A2 , λ _B2 , λ _C2 , λ _D2 , λ _A3 , λ _B3 , λ _C3 , λ _D3 are all different wavelengths. .

The wavelength multiplexed signal from the optical coupler (Coupler) 23 is transmitted to the switching center 10 through the optical fiber 20. Although not specifically shown, if the optical signal is attenuated due to a long transmission distance, an optical amplifier is inserted in the middle of the transmission path to the switching center, or compensated if the optical dispersion is large. A dispersion compensator may be inserted. The processing of the wavelength multiplexed signal in the switching center 10 has already been described above, and the finally multiplexed wavelength multiplexed signals λ _{A to D} are sent to each point via each optical fiber 21.

The wavelength selector F at each point selects an optical signal having a wavelength including a moving image to be displayed on each display 6 from the received wavelength multiplexed signals λ _{A to D.} For example, at the point A, the wavelength selector F _B3 is one of the three optical signals λ _B1 , λ _B2 , λ _B3 corresponding to the moving image signals captured by the three video cameras 5 at the point B (for example, the point The optical signal λ _B3 ) of the video camera on the right side of B is selected. Similarly, the wavelength selector F _C2 selects one of the three optical signals λ _C1 , λ _C2 , and λ _{C3 from} the point C (for example, the optical signal λ _C2 of the video camera in the center of the point C), and the wavelength. The selector F _D1 selects one of the three optical signals λ _D1 , λ _D2 , and λ _{D3 from} the point D (for example, the optical signal λ _D1 of the video camera on the left side of the point D). That is, the three optical signals selected by the three wavelength selectors at the point A are selected so that the positions (left, center, right) of the three video cameras at the other points B to D, in other words, the shooting directions are different. Is done. The other points B to D are similarly selected. An optical filter can be used for the wavelength selector F, or an AWG (Arrayed Waveguide Grating) may be used. Each selected optical signal is converted into a drive signal that can be displayed on the corresponding display 6 by the optical receiver R, and displayed as a moving image at another point on each display.

In this way, for example, the image seen by the person (A) at the point A is displayed on the left display of the person (B) at the point B taken from the right side when viewed from (B). The front display shows a person at point C (an image of C taken from the front, and the right display shows an image of the person at point D (D) taken from the left as viewed from (D). By doing in this way, it is possible to realize a meeting with a sense of reality that makes it possible for each of the four conference participants 7 to gather at the same place and feel that their opponents exist on the left, front, and right. Although not shown, the incoming optical signal includes the image signal at the point, so if necessary, select it with the wavelength selector and send it to the other party using a separate display. It is also possible to monitor the appearance of yourself A.

When conducting a video conference, it is assumed that there is not always a fixed point. That is, for example, in the video conference system of the embodiment of FIG. 3, (a) a meeting is held at four points of point A, point B, point C, and point D when (a) is present, and (b) It can be assumed that a conference is held at two points and another conference is held at two points of points C and D at the same time. The case of (a) is a case where the connection of the optical matrix switch 14 of FIG. 4 mentioned above is used, for example. In the case (b), for example, as shown in FIG. 5, the connection of the optical matrix switch 14 is changed to IN5 → OUT6.
IN6 → OUT5
IN7 → OUT8
IN8 → OUT7
Then, a desired connection can be realized.

In this way, it becomes possible to switch the locations participating in the conference using the optical switch. These controls are performed using a controller in the exchange. The controller of the switching center and the controller at each point need to operate in a coordinated manner, and there is a method of connecting using the Internet or an intranet which is a separate line from moving image transmission. Alternatively, even when the same optical fiber connection is used, for example, a moving image transmission may use a 1.5 μm band optical signal, and a control signal between controllers may use a 1.3 μm band optical signal. In this way, a video conference can be performed by instructing the system of the controller connected in cooperation to commands such as conference reservation, connection, and disconnection by an appropriate method.

In the above description, the case where the wavelength on the transmission side is fixed and the wavelength in the pass band of the wavelength selector F on the reception side is made variable to select a desired signal has been described. In order to make an equivalent connection, the wavelength selector F on the reception side may be fixed, the wavelength on the transmission side, that is, the video camera 5 side may be variable, and the wavelength may be selected and transmitted so as to appear on the desired display 6. . In general, an optical filter (wavelength tunable filter) used as the wavelength selector F is more expensive than a wavelength tunable light source, so it is useful to make the transmission side variable.

As described above, on the premise that the wavelength of the wavelength selector F on the receiving side is fixed and the wavelength on the transmitting side is variable, the wavelength used for the multi-point conference (for example, four points) is determined as the specific wavelength. When using a three-sided display as in the example of FIG. 3, the number of specific wavelengths is “number of points × number of displays”, that is, 4 × 3 = 12 wavelengths. When participating in a conference at a plurality of points, the transmission wavelength from each video camera 5 is assigned to one of the specific wavelengths under the control of the controller 25. Since the wavelength selector F on the receiving side is fixed to a specific wavelength for the conference, a multi-point conference can be executed. In order to enable the system to function even when it is desired to hold another conference without participating in this multi-point conference, the wavelength of the wavelength selector F on the reception side associated with the display 6 is used. Allows a wavelength other than the specific wavelength assigned for the conference at a plurality of points to pass. Since switching is performed by the optical matrix switch 14, the signals of the conferences at a plurality of points are not mixed at this time. That is, users participating in a conference at a plurality of locations use a specific wavelength of 12 wavelengths in this example, and users who do not participate in a conference at a plurality of locations use other wavelengths.

If the transmission wavelength is variable and the reception wavelength is fixed to a specific wavelength, it becomes possible to provide services to a large number of users. That is, it is possible to accommodate as many users as the number of ports of the optical matrix switch 14 allows for a larger number of users than the wavelength used for a multipoint conference or other conference. On the other hand, when the transmission wavelength is fixed, the upper limit of the number of users is further limited by the number of wavelengths that can be set by the wavelength selector F on the receiving side. It is also possible to make the wavelength selection more flexible by making the optical wavelength on the transmission side variable and simultaneously changing the wavelength of the wavelength selector F on the reception side. That is, the transmission side wavelength and the wavelength of the wavelength selector F on the reception side are operated under the control of the controller 25 so as to use the empty wavelength.

In the video conference system of FIG. 3, only the moving image is shown, but the audio can be transmitted in the same manner. That is, sound is converted into an electrical signal with a microphone installed at each point, the transmission of the sound signal is superimposed on the moving image signal, and the sound signal is separated from the moving image signal at the receiving point and is made sound with a speaker. It can be easily realized by conventional techniques such as. The microphone may be either a built-in (accompanying) type of the video camera 5 or a stand-alone type. The speaker may be either a stand-alone type or a built-in (accompanying) type of the display 6. In this way, a video conference between a plurality of points can be realized by transmitting moving images and sound between the plurality of points.

In the above description, it has been described that the optical signal from each point is directly connected to the exchange, but in reality, the same route may be taken from the middle. For example, when the point A and the point B are in a relatively close area, the optical signal from the point A and the optical signal from the point B take the same route between the relay station and the exchange station provided in the middle of each route. This is the case. In that case, the optical multiplexer and the optical demultiplexer that handle the optical signals from each point are not installed only in the exchange, but some functions thereof, that is, the optical multiplexer and the optical demultiplexer related to the points A and B Can be installed at the relay station. By doing so, the number of optical fibers secured between the relay station and the exchange station can be further reduced.

Furthermore, in the above description, the image captured by the video camera is described as the high-definition moving image generated at each point. However, during the course of the conference, for example, a high-definition image (still image or moving image) generated by a computer, A high-definition image source (for example, a video recording device, etc.) can be connected and used for explanation. Switching between the high-definition moving image captured by the video camera and the source of these high-definition video can be realized by using the conventional technology, and transmission of this to multiple points can also be realized by the method of the present invention. In this case, the audio information can be superimposed on a high-definition image in the same manner as in the case of a video camera using the conventional technology.

Second Embodiment
FIG. 6 is a diagram showing an overall configuration of a video conference system according to another embodiment of the present invention. In the video conference system 110 in FIG. 6, the video cameras 5 at each of the points A to D (1 to 4) are limited to one, and the moving image signal sent to the exchange 10 is limited to one. The optical transmitter T at each point converts a moving image signal from one video camera 5 into an optical signal and sends the optical signal to the exchange 10 via the optical fiber 20. Unlike the case of FIG. 3, an optical coupler is not necessary. Other configurations and operations thereof are basically the same as those in the configuration of FIG.

The optical signal sent from each point A to D to the switching center 10 is not a wavelength multiplexed signal but a single wavelength optical signal. Also in this case, the wavelength of the optical signal sent from each point to the exchange is different. That is, the optical wavelength of the signal sent from the point A to the exchange is λ _A , the optical wavelength of the signal sent from the point B to the exchange is λ _B , the optical wavelength of the signal sent from the point C to the exchange is λ _C , and the signal is exchanged from the point D When the optical wavelength of the signal sent to the station is λ _D , λ _A , λ _B , λ _C , and λ _D are all different. Although not shown in the figure, an optical amplifier is inserted in the middle of the transmission path when the optical signal is attenuated due to a long transmission distance, or a dispersion compensator is inserted to compensate for it when the optical dispersion is large. Just do it. As in the case of FIG. 3, the optical signal sent to the switching center is multiplexed by a multiplexer to become wavelength multiplexed signals λ _{A to D} including wavelengths λ _A , λ _B , λ _C , λ _D , It is sent to each point via the fiber 21.

The wavelength multiplexed signals λ _{A to D} arriving at the respective points select optical signals having wavelengths including moving images to be displayed on the respective displays 6 by the wavelength selector F. For example, the point A, the wavelength selector F _B selects an optical signal lambda _B corresponding to the moving image signal is a video camera 5 point B taken. Likewise, wavelength selector F _C selects the optical signal lambda _C from the point C, the wavelength selector F _D selects the optical signal lambda _D from the point C. The other points B to D are similarly selected. An optical filter can be used for the wavelength selector, or an AWG (Arrayed Waveguide Grating) may be used. Each selected optical signal is converted into a drive signal that can be displayed on the corresponding display 6 by the optical receiver R, and displayed as a moving image at another point on each display.

<Third Embodiment>
In the embodiment described above, a system for connecting four points has been described. In general, a conference system that connects more points can be considered. In that case, the number of points can be expanded to more than four points by the method described above. That is, the number of ports of the optical matrix switch 14 in FIG. 3 may be increased. On the other hand, there may be a case where the number of displays 6 that can be arranged at each point is limited, or a case where the maximum number of points is limited as a conference policy. FIG. 7 shows a configuration example regarding such a case, where the number of points is 12 and the number of points that can participate in a multi-point conference is limited to 4 points. Here, a 16-input (IN) × 16-output (OUT) optical matrix switch 14 is used.

The optical signals from the points participating in the multipoint conference are switched to the input of the optical coupler 16 by the optical matrix switch 14. The wavelength multiplexed signal of the optical demultiplexer (Distributor) 18 after passing through the optical amplifier 12 is switched so as to be connected to the participation point. Furthermore, it is possible to hold a conference between two points by connecting points that do not participate in the conference of the plurality of points at the same time via the optical matrix switch 14. For example, by performing a connection as in the optical matrix switch 14 of FIG. 7, while a meeting is held at four points of point A, point B, point C, and point D, two points E and Z are simultaneously displayed. Conferences can be held between points.

In this way, when the counterpart point displayed on each display changes, it is necessary to control the wavelength of the wavelength selector F disposed in front of the optical receiver R so as to match the wavelength of the counterpart. Such a wavelength selector F can be realized using, for example, a conventional wavelength tunable filter. This wavelength control is executed under the control of the controller 25. In the third embodiment shown in FIG. 7, since the points participating in a certain conference and the points not participating in the conference are separated by the optical matrix switch 14, the confidentiality of the content of the conference can be maintained. That is, since information on the conference is not sent to a point not participating in the conference, it is not possible to intentionally eavesdrop, so security is ensured.

<Fourth embodiment>
In the configuration of FIG. 7, the number of simultaneous multi-point (three or more) meetings is limited to one. Therefore, as shown in FIG. 8, by arranging a plurality of sets of optical multiplexers (Couplers) 16, optical amplifiers 12, and optical demultiplexers (Distributors) 18, the number of simultaneous meetings held at a plurality of points can be determined. The number can be increased up to two (two or more).

<Fifth Embodiment>
In the video conference system according to the embodiment of FIG. 3 or FIG. 6, in order to make the optical fiber connecting each point and the switching center into one single-core common optical fiber 24, as shown in FIG.

Circulators

8 and 13 are installed at each point and exchange. That is, at each point, the optical signal from the optical coupler (Coupler) 25 or the transmitter T is input to the optical circulator 8 and transmitted only to the common port side. The optical signal from the common port side of the optical circulator 8 is output only to the wavelength selector F side. In the switching center 10, the optical signal from the common port side of the optical circulator 13 is output only to the optical coupler (Coupler) 16 side, and the optical signal from the optical demultiplexer (Distributor) 18 is output only to the common port side. Is done.

Although omitted in FIG. 9, a similar optical circulator can be selectively introduced in an optical fiber line connecting another point (one or more) and the exchange. By configuring in this way, the number of optical fibers connecting each point and the exchange is reduced from two to one, and the cost can be reduced. In addition, when an optical amplifier is inserted in the middle of the transmission path in order to compensate for the attenuation of the optical signal due to the long transmission distance in the optical transmission line described above, an optical circulator is disposed before and after the optical path. Separate and amplify the light in the transmission direction.

Also, as shown in FIG. 10, it is possible to reduce the number of optical circulators using an optical filter. (A) it is without providing the optical circulator at each point, the optical multiplexer 15, a case where the transmitting-side optical filter F _x, provided the reception side optical filter F _Y. (B) it is without providing the optical circulator in the exchange station 10, the optical multiplexer 15, a case where the transmitting-side optical filter F _x, provided the reception side optical filter F _Y. (C) is without providing the optical circulator at each point, the optical multiplexer 15, a case in which the receiving-side optical filter F _Y. (D) is without providing the optical circulator in the exchange station 10, the optical multiplexer 15, a case in which the transmitting-side optical filter F _x. The optical filters F _x and F _Y are set so as to pass an optical signal having a desired wavelength or to block unnecessary optical signals. The receiver-side optical filter F _Y can be substituted by already optical filter wavelength selector F of each point in FIG. 3 described. In general, it is desirable to use a circulator because there is a fundamental loss in optical couplers, and there are restrictions on the optical filter's passing loss and unwanted wave blocking capability. However, it is possible to reduce the number of optical circulators by appropriate design judgment. It is.

<Sixth Embodiment>
The embodiment (application example) of the present invention can be considered not only as a video conference as shown in FIG. FIG. 11 shows a configuration example in the case of implementation as a so-called video wall system. As shown in (a), two remote connections between point A, point B, point C, and point D are mutually connected so that a person stands in front of each display and talks with the person at the other point independently. In other words, a situation is shown in which six conversations are made between four points. The video wall is always connected regardless of whether people are present or not. If six people at positions A1-B3, A2-C2, and C3-B1 want to talk together from the state of (a), B2 and D2 have another conversation as shown in (b) The video will be in the way. Therefore, as shown in (c), it is desirable to change the pair of the video camera and the display by changing the positions of B1 and B2. For this purpose, an instruction is sent via a controller 25 (see FIG. 3; the same applies hereinafter) to exchange the output wavelength of the video camera 5 or the wavelength of the optical filter F on the display 6 side. That's fine. After the discussion of the six people, whether to return to the original state or keep the last state may be determined by the individual operation policy. Further, in the video wall, it is possible to change the communication partner by installing the optical matrix switch 14 in the exchange as shown in FIG. In this way, the configuration of the present invention can be applied to a video wall whose principle is always-on connection, and flexible operation is possible in addition to simple functions.

The embodiment of the present invention has been described with reference to the drawings. However, the present invention is not limited to these embodiments. Furthermore, the present invention can be implemented in variously modified, modified, and modified forms based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

The video conference system of the present invention is not limited to video conferences that connect conference rooms, but also high-definition images such as music ensembles, remote lectures, medical applications, multiple work sites and their consoles, etc., with low delay, that is, in real time. It can be widely applied to the case where it is effective to create a realistic situation where three or more remote locations are in the immediate vicinity.

1, 2, 3, 4 points 5 Video camera 6 Display 7 (Meeting participants)
8, 13

Optical circulator

10, 31

Switching office

11, 25

Controller

12, 34 Optical amplifier 14

Optical matrix switch

15, 16, 23, 30, 33

Optical multiplexer

18, 32, 35

Optical demultiplexer

20, 21, 24 Light fiber
100, 110 video conferencing system

Claims

A video conferencing system that uses an optical path network that connects a plurality of points bidirectionally via optical fibers via at least one exchange,
At each point
Multiple video cameras,
Multiple displays,
An optical transmitter for converting each of the moving image signals from the plurality of video cameras into optical signals of different wavelengths assigned to the video cameras;
A first optical multiplexer that multiplexes optical signals of different wavelengths from the optical transmitter and outputs them as a first wavelength multiplexed signal to an exchange via an optical fiber;
A first wavelength selector for demultiplexing and outputting a second wavelength multiplexed signal including an optical signal from a point other than the point sent from the exchange via an optical fiber;
A first optical receiver that converts each of the optical signals from the first wavelength selector into a driving signal for displaying a moving image on a corresponding display;
The exchange is
A third optical multiplexer that multiplexes each of the first wavelength multiplexed signals transmitted from each point and outputs the multiplexed signal as a third wavelength multiplexed signal;
An optical demultiplexer that outputs the third wavelength multiplexed signal from the third optical multiplexer toward each of the optical fibers connected to each point;
In order to send the first wavelength multiplexed signal transmitted from each point to a selected point, the input of the first wavelength multiplexed signal to the third optical multiplexer is switched, and the optical demultiplexer An optical matrix switch that switches an output of the third wavelength multiplexed signal to an optical fiber connected to a point.
A video conferencing system that uses an optical path network that connects a plurality of points bidirectionally via optical fibers via at least one exchange,
At each point
At least one video camera;
Multiple displays,
An optical transmitter that converts a moving image signal from the video camera into a first optical signal having a wavelength assigned to the video camera, and transmits the first optical signal to an exchange through an optical fiber;
A second wavelength selector for demultiplexing and outputting a second wavelength multiplexed signal including an optical signal from a point other than the point sent from the exchange via an optical fiber;
A second optical receiver that converts each of the optical signals from the second wavelength selector into a driving signal for displaying a moving image on a corresponding display;
The exchange is
A third optical multiplexer that multiplexes each of the first optical signals transmitted from each point and outputs a third wavelength multiplexed signal;
An optical demultiplexer that outputs the third wavelength multiplexed signal from the third optical multiplexer to each of the optical fibers connected to each point;
In order to send the first wavelength multiplexed signal transmitted from each point to a selected point, the input of the first wavelength multiplexed signal to the third optical multiplexer is switched, and the optical demultiplexer An optical matrix switch that switches an output of the third wavelength multiplexed signal to the optical fiber connected to a point.
The optical fiber comprises a single core common optical fiber,
At each point, the first wavelength multiplexed signal from the first optical multiplexer is output to the common optical fiber, and the second wavelength multiplexed signal transmitted through the common optical fiber is output to the first optical multiplexer. The video conferencing system according to claim 1, further comprising an optical circulator that outputs to one wavelength selector.
The optical fiber comprises a single core common optical fiber,
At each point, the first optical signal from the optical transmitter is output to the common optical fiber, and the second wavelength multiplexed signal transmitted through the common optical fiber is selected as the second wavelength selection signal. The video conferencing system of claim 2, further comprising an optical circulator that outputs to the instrument.
The switching center outputs the first wavelength multiplexed signal transmitted via the optical fiber to the third optical multiplexer, and the third wavelength multiplexed signal from the optical demultiplexer is output to the optical fiber. The video conferencing system of claim 3, further comprising an optical circulator that outputs to.
The switching center outputs the first optical signal sent via the optical fiber to the third optical multiplexer, and the third wavelength multiplexed signal from the optical demultiplexer to the optical fiber. 5. The video conferencing system of claim 4, further comprising an optical circulator for outputting.
3. The video conference system according to claim 1, wherein the exchange further includes an optical amplifier that amplifies the third wavelength multiplexed signal from the third optical multiplexer and sends the amplified signal to the optical demultiplexer.
The video conferencing system according to claim 1 or 2, wherein the switching center is provided with a plurality of sets of the third optical multiplexer and the optical demultiplexer.