JP2007329585A - Optical transmission system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical transmission system capable of transmitting NRZ signals as many as possible through one optical transmission line in order to address requirements of high speed/high capacity. <P>SOLUTION: A transmission apparatus in the optical transmission system is provided with: a plurality of light emitting elements transmitting optical signals through the optical signal transmission line; and a control circuit for determining turning on/off of each light emitting element on the basis of the NRZ signals being objects of transmission. The signal strength values of lights emitted from the light emitting elements are, for example, different from each other, and determined on the basis of a strength value whereby a plurality of optional strength values associated with a sum of the optional strength values are uniquely determined. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical transmission system for transmitting an optical signal.

  2. Description of the Related Art A transmission system that transmits a signal (NRZ signal) based on a NRZ (Non-Return Zero) code, which is general as digital data, is used for information transmission between various information processing apparatuses or inside an information processing apparatus. For example, in an image forming apparatus such as a printer, the amount of data to be transmitted inside the apparatus is large, so that a transmission system with high speed and high capacity is required.

  Therefore, use of an optical transmission system having a relatively high speed and a large capacity is being studied. In an optical transmission system, a light emitting device and a light receiving device are generally connected via an optical signal transmission path such as an optical fiber, the light emitting device is controlled to emit light based on an NRZ signal, and an optical signal received on the light receiving device side is converted. Based on this, the NRZ signal is decoded.

Here, in the optical transmission system, the frequency of the NRZ signal is determined based on a request such as a transmission rate, but usable light-emitting devices and light-receiving devices are limited due to frequency response characteristics. As a specific example, a general LED (light emitting diode) or the like has only a frequency characteristic capable of supporting a transmission rate of about 100 megabits per second, but a surface emitting laser or the like has a transmission rate of about 3 gigabits per second. Some have frequency characteristics that can be supported.
JP 2003-258722 A

  However, light-emitting devices with frequency characteristics corresponding to relatively high transmission rates are more expensive than light-emitting devices with only frequency characteristics corresponding to relatively low transmission rates, and are inexpensive and have high transmission. There has been a demand for an optical transmission system capable of handling the rate.

  Here, for example, with respect to two NRZ signals synchronized in clock, one NRZ signal is converted by a logical product with the clock signal to obtain a first RZ signal, and the other NRZ signal is inverted from the clock. Patent Document 1 discloses a system that obtains a second RZ signal converted by a logical product with a signal, combines the first and second RZ signals, and transmits the resultant signal through one optical transmission line. .

  However, this technique can only transmit at most two NRZ signals via one optical transmission line, and cannot sufficiently meet the demand for high speed and high capacity.

  The present invention has been made in view of the above circumstances, and an optical transmission capable of transmitting more signals through one optical transmission line in response to a demand for high speed and high capacity while using an inexpensive light emitting device. One of its purposes is to provide a system.

  The present invention for solving the problems of the above-described conventional example is an optical transmission system including a transmission-side device and a reception-side device that are connected to each other via an optical signal transmission line, and the transmission-side device includes: A plurality of light emitting elements that transmit an optical signal through an optical signal transmission path, a control circuit that determines whether each light emitting element is turned on or off based on a signal to be transmitted, and a clock signal for each of the light emitting elements. A first group that emits light for a half period of the clock signal from a predetermined phase of the clock signal and a second group that emits light at a time shifted by a half period from the predetermined phase of the clock signal and emits light for the half period of the clock signal. If there is a light emitting element that belongs to the first group and should be turned on by the control circuit, it emits light for a half period of the clock signal from a predetermined phase of the predetermined clock signal, and belongs to the second group. If there is a light emitting element to be turned on by the control circuit, a drive circuit that emits light from a point shifted by a half cycle from the predetermined phase of the clock signal, and emits light for a half cycle of the clock signal, and The receiving side device receives a light signal coming via the optical signal transmission path and converts it into an electrical signal, and determines whether each light emitting element of the transmitting side device is turned on or off based on the electrical signal. And a decoding circuit for decoding the signal to be transmitted.

  In addition, the present invention for solving the problems of the above-described conventional example is a transmission device, which is based on a plurality of light emitting elements that transmit an optical signal through an optical signal transmission path and a signal to be transmitted. A control circuit that determines whether each light emitting element is turned on or off; a first group that emits light for a half period of the clock signal from a predetermined phase of the clock signal; and a half period from the predetermined phase of the clock signal. If there is a light emitting element that belongs to the first group and is to be turned on by the control circuit, the predetermined clock signal is emitted. If there is a light emitting element that emits light for a half period of the clock signal from the predetermined phase and belongs to the second group and should be lit by the control circuit, the predetermined position of the clock signal Emitted from the time shifted by more half cycle, and a drive circuit for the light emitting by a half period of the clock signal, comprising the.

  Here, the drive circuit has different intensity values of light emitted from each light emitting element, and a plurality of intensity values related to the sum based on a sum of a plurality of arbitrary intensity values. The light emitting element may be determined based on a uniquely determined intensity value, and each light emitting element may be controlled to emit light based on the determined intensity value.

  In this case, approximately half of the light sources with the determined low intensity values may be light emitting elements belonging to the second group.

  Further, one embodiment of the present invention is a transmitting device, in which a plurality of light emitting elements that transmit an optical signal via an optical signal transmission path, and lighting and extinguishing of each light emitting element based on a signal to be transmitted. Based on the sum of a plurality of arbitrary intensity values, the intensity values related to the sum are uniquely determined based on the control circuit to be determined and the signal intensity of the light emitted from each light emitting element. And a drive circuit that emits light from a light-emitting element that is determined to be lit by the control circuit according to the determined intensity value.

  According to another aspect of the present invention, there is provided an optical signal transmission method based on a signal to be transmitted using a transmission device including a plurality of light emitting elements that transmit an optical signal via an optical signal transmission path. A step of determining whether each light emitting element is turned on or off, a first group that emits light for a half period of the clock signal from a predetermined phase of the clock signal, and a half period from the predetermined phase of the clock signal. If there is a light-emitting element that belongs to the first group and should be turned on, it emits light from the point of time shifted by a half period of the clock signal. If there is a light emitting element that emits light for a half cycle of the clock signal and belongs to the second group and is to be lit, the light is emitted from a point shifted by a half cycle from the predetermined phase of the clock signal. It is characterized by comprising a step of emitting by a half period of the click signal.

  Embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, an optical transmission system according to an embodiment of the present invention includes a transmission device 1, a reception device 2, and an optical fiber 3 that is an optical signal transmission path connecting them. The

  The transmission device 1 also includes a control unit 11, a driver unit 12, a light emitting element array 13, and a coupling unit 14, and the reception device 2 includes a light receiving unit 21, a decoding unit 22, and a control unit 23. Consists of including. In the transmission apparatus 1 of the present embodiment, the light emitting element array 13 includes a plurality (n) of light emitting elements.

  The control unit 11 of the transmission device 1 is a microcomputer or the like, and generates n (n bits) NRZ signals based on data to be transmitted and outputs the NRZ signals to the driver unit 12.

  As illustrated in FIG. 2, the driver unit 12 includes a clock signal generation unit 31, a logical operation unit 32, and a current control unit 33. The clock signal generation unit 31 generates and outputs a rectangular wave signal having a predetermined frequency. This frequency is set to be less than ½ of the maximum response frequency of the light emitting elements included in the light emitting element array 13.

  The logical operation unit 32 includes n / 2 buffers Bp, n / 2 inverting buffers (NOT circuits) Bn, and n AND circuits L provided corresponding to any of these. Each of the buffers Bp of the logical operation unit 32 outputs a clock signal to the corresponding AND circuit L. The AND circuit L calculates the logical product of the value input from the buffer Bp and the corresponding bit in the data represented by the NRZ signal, and outputs the logical product to the current control unit 33. That is, the group of light emitting elements whose lighting is controlled by the output of these AND circuits L belongs to the first group that emits light for a half cycle of the clock signal from a predetermined phase (the rising phase here) of the clock signal.

  The inversion buffer Bn inverts the clock signal and outputs it to the corresponding AND circuit L. The AND circuit L calculates the logical product of the value input from the buffer Bn and the corresponding bit in the data represented by the NRZ signal, and outputs the logical product to the current control unit 33. That is, the group of light-emitting elements whose lighting is controlled by the output of these AND circuits L emits light for a half cycle of the clock signal from the time when it deviates from the predetermined phase of the clock signal by a half cycle (here, the time of falling). Belongs to the second group.

  When n is an odd number, the number of buffers Bp is (n + 1) / 2 (or (n-1) / 2), and the number of inversion buffers Bn is (n-1) / 2 (or ( n + 1) / 2).

  The current control unit 33 is provided corresponding to each bit of the data represented by the NRZ signal, and the signal input from the AND circuit L of the logic operation unit 32 that performs the operation related to the corresponding bit is at the “H” level. In this case, a preset current amount corresponding to each bit is output to the corresponding light emitting element of the light emitting element array 13.

  Each light emitting element of the light emitting element array 13 emits light with a current output from the corresponding current control unit 33. In the present embodiment, the light emitting element is an LED (light emitting diode), and the current control unit 33 varies the amount of current for each LED within the dynamic range Δ of the light emission intensity of the LED that is the light emitting element. One of the characteristic features of the present embodiment is that the emission intensity of each LED is different from each other and based on the sum of a plurality of arbitrary intensity values, a plurality of intensities related to the sum. The value is determined based on an intensity value that is uniquely determined.

を単位ｅとして、強度値が１ｅ，２ｅ，４ｅ，８ｅ…のいずれかに定められているとすれば、各ＬＥＤの点灯時の発光強度が１ｅ，２ｅ，４ｅ，８ｅ…となるよう、電流制御部３３が供給する電流量が予め設定される。 For example,

If the intensity value is set to any one of 1e, 2e, 4e, 8e..., The current intensity is 1e, 2e, 4e, 8e. The amount of current supplied by the control unit 33 is set in advance.

  As a result, for example, when an LED defined as the intensity 1e or 2e is lit, an optical signal having an intensity 3e is output. On the side receiving the optical signal having the intensity 3e, It can be detected that the LEDs 1e and 2e are lit.

  The coupling unit 14 couples light emitted from each light emitting element in the light emitting element array 13 and guides the light into the optical fiber 3 that is an optical transmission path. That is, the optical fiber 3 transmits light having an intensity corresponding to the sum of the emission intensity of the LEDs emitting light in the light emitting element array.

  The light receiving unit 21 of the light receiving device 2 is an optical sensor or the like, and generates an electric signal representing the intensity of the optical signal transmitted through the optical fiber 3. Based on the electrical signal generated by the light receiving unit 21, the decoding unit 22 generates and outputs a signal (decoded signal) indicating which light emitting element is turned on and off in which transmission device 1. The control unit 23 generates and outputs data to be transmitted based on the decoded signal.

  The optical transmission system according to the present embodiment is configured as described above and operates as follows. In the following description, for simplicity of explanation, the light emitting element array 13 is provided with four LEDs as light emitting elements from D1 to D4, and the intensity value of D1 is 1e and the intensity value of D2. Is 2e, the intensity value of D3 is set to 4e, and the intensity value of D4 is set to 8e. In addition, approximately half (in this case, two of D1 and D2) from the low intensity values are light emitting elements belonging to the first group. This makes it easier to output a relatively high-brightness optical signal in the half cycle (first half-cycle) from the falling edge of the clock, and a relatively low-brightness optical signal in the half cycle (second half cycle) from the rising edge of the clock. This makes it easy to perform processing using this difference in intensity. However, D1 and D4 may belong to the first group and D2 and D3 may belong to the second group so that the luminances of the first half cycle and the second half cycle of the clock are as close as possible. Furthermore, only D4 may belong to the first group, and D1, D2, and D3 may belong to the second group.

  In the following example, it is assumed that data to be transmitted is “0xE9, 0x70, 0xFC, 0x01...” (0x indicates a hexadecimal number). Here, “0xE9” can be represented by two 4-bits as “1110, 1001” in binary number, and in the transmission system of the present embodiment, a 4-bit signal per clock cycle is generated by four LEDs. Send.

  The control unit 11 generates a 4-bit NRZ signal based on data input as an object to be transmitted. Here, the NRZ signal becomes “111010010111...” Based on the binary representation of the data.

  The clock signal generator 31 of the driver unit 12 outputs a clock signal as shown in FIG. The logic operation unit corresponding to the light emitting element D1 includes an AND circuit L that calculates a logical product of the clock signal and the corresponding bit of the NRZ signal. Accordingly, the light emitting element D1 emits light during a period in which the clock signal is at the “H” level when the corresponding bit is “1” (assumed to be at the “H” level). The same applies to the light emitting element D2.

  The logic operation unit corresponding to the light emitting element D3 is a logic of the inversion buffer Bn that inverts and outputs the corresponding bit of the clock signal, the inverted clock signal, and the corresponding bit of the data represented by the NRZ signal. An AND circuit L for calculating the product is included. Accordingly, the light emitting element D3 emits light during a period in which the clock signal is at the “L” level when the corresponding bit is “1” (assumed to be at the “H” level). The same applies to the light emitting element D4.

  As already described, when the light emitting elements D1 to D4 are each instructed to emit light by the logic operation unit 32, the current control unit 33 is controlled to emit light at the light emission intensities 1e, 2e, 4e, and 8e, respectively. .

  In the case of the above-mentioned data “0xE9, 0x70, 0xFC, 0x01...”, The original “E” data is divided into the first half 2 bits “11” and the second half 2 bits “10”. Based on the above, the light emitting elements D3 and D4 are controlled to be lit in the first half cycle of the clock. During this period, the light emitting elements D1, D2 are turned off. Further, only the light emitting element D2 is controlled to be turned on and the light emitting elements D1, D3, and D4 are turned off based on the data for the latter half 2 bits. As a result, an optical signal having an intensity of 4e + 8e = 12e is transmitted through the optical fiber 3 in the first half cycle of the clock, and an optical signal having an intensity of 2e is transmitted through the optical fiber 3 in the second half cycle of the clock.

  Similarly, only the light emitting element D4 is controlled to be turned on in the first half cycle of the next clock, and only the light emitting element D1 is controlled to be turned on in the second half period. As a result, an optical signal having an intensity of 8e is transmitted through the optical fiber 3 in the first half period of the clock, and an optical signal having an intensity of 1e is transmitted through the optical fiber 3 in the latter half period of the clock.

  That is, the intensity of the optical signal transmitted by the optical fiber 3 is as shown in FIG.

  The receiving device 2 generates information indicating the intensity of the optical signal transmitted through the optical fiber 3. From the above-mentioned example, the information of the intensity | strength of 12e, 2e, 8e, 1e ... is produced | generated for every time for the half cycle of a clock.

  The decoding unit 22 of the receiving device 2 obtains the sum of information for one cycle. Here, information of “12e + 2e = 14e” in the first period and “8e + 1e = 9e” in the second period are obtained. And the lighting / extinguishing state of each light emitting element D1 to D4 in the transmission apparatus 1 is determined from these pieces of information. In the case of 14e, since the light emission intensity of each light emitting element is 1e, 2e, 4e, and 8e, it is determined that 14e = 2e + 4e + 8e, and the light emitting elements D2, D3, and D4 are turned on, that is, the data is It is determined that it was “1110”. The decoding unit 22 generates and outputs the NRZ signal “1110...” Based on the determination result.

  Based on the NRZ signal output from the decoding unit 22, the control unit 23 reproduces and outputs “0xE9...” As data to be transmitted.

  According to the present embodiment, a plurality of bits of data are generated in one clock using a number of light emitting elements that are within the dynamic range of the light emission intensity of the light emitting elements and can be set to different values that can be resolved from the sum. Thus, more NRZ signals can be transmitted through one optical transmission line in response to the demand for higher speed and higher capacity while using an inexpensive light emitting device such as an LED.

  In the above description, the data capacity that can be transmitted is increased by transmitting different signals in the first half cycle and the second half cycle of the clock signal. Based on each bit of the data represented by the NRZ signal, the corresponding light emitting element may be controlled to emit light as it is. In this case, among the light emitting elements included in the light emitting element array 13 among the light emitting elements included in the light emitting element array 13, the light emitting elements corresponding to the bits that are “1” among the bits of the data represented by the NRZ signal are turned on. Optical signals with different intensities emitted by the light emitting elements that are lit are transmitted through the optical fiber 3.

  In the description so far, the NRZ signal has been described as an example of the signal that changes in the cycle of the clock signal. However, the present invention is not limited to this, and for example, the signal value is “1” or “−” like the NRZI signal. 1 "may be used.

1 is a configuration block diagram of an optical transmission system according to an embodiment of the present invention. It is a block diagram showing the example of a structure of the logical operation part of the transmitter which concerns on embodiment of this invention. It is a timing chart figure showing the example of the luminescence situation of the light emitting element in the optical transmission system concerning an embodiment of the invention, and the signal transmitted.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Transmitter, 2 Receiver, 3 Optical fiber, 11, 23 Control part, 12 Driver part, 13 Light emitting element array, 14 Coupling part, 21 Light receiving part, 22 Decoding part, 31 Clock signal generation part, 32 Logic operation part, 33 Current controller.

Claims (6)

An optical transmission system including a transmission-side device and a reception-side device connected to each other via an optical signal transmission path,
The transmitting device is:
A plurality of light emitting elements that transmit an optical signal via an optical signal transmission path;
A control circuit that determines whether to turn on or off each light emitting element based on a signal to be transmitted;
Each of the light emitting elements emits light from a first group that emits light for a half period of the clock signal from a predetermined phase of the clock signal, and light emitted from a point that is shifted by a half period from the predetermined phase of the clock signal. If there is a light emitting element that belongs to the first group and is to be turned on by the control circuit, it emits light for a half period of the clock signal from a predetermined phase of the predetermined clock signal, If there is a light emitting element that belongs to the second group and is supposed to be turned on by the control circuit, a drive that emits light from a point shifted by a half cycle from the predetermined phase of the clock signal and emits light for a half cycle of the clock signal Circuit,
With
The receiving side device
A light receiving element that receives an optical signal arriving via an optical signal transmission path and converts it into an electrical signal;
Based on the electrical signal, a determination circuit that determines whether each light emitting element of the transmission side device is turned on and off, and a decoding circuit that decodes a signal to be transmitted;
An optical transmission system comprising: A plurality of light emitting elements that transmit an optical signal via an optical signal transmission path;
A control circuit that determines whether to turn on or off each light emitting element based on a signal to be transmitted;
Each of the light emitting elements emits light from a first group that emits light for a half period of the clock signal from a predetermined phase of the clock signal, and light emitted from a point that is shifted by a half period from the predetermined phase of the clock signal. If there is a light emitting element that belongs to the first group and is to be lit by the control circuit, it emits light for a half period of the clock signal from a predetermined phase of the predetermined clock signal, If there is a light emitting element that belongs to the second group and is to be turned on by the control circuit, a drive that emits light from a point shifted by a half cycle from the predetermined phase of the clock signal and emits light for a half cycle of the clock signal Circuit,
A transmission device comprising: The transmission device according to claim 2,
The drive circuit determines the signal intensity of light emitted by each light emitting element,
Different intensity values,
In addition, based on the sum of a plurality of arbitrary intensity values, a plurality of intensity values related to the sum are uniquely determined, and the light emission of each light emitting element is controlled based on the determined intensity value. A transmitting device. The transmission device according to claim 3,
A transmitting apparatus characterized in that substantially half of the determined intensity values are the light emitting elements belonging to the second group. A plurality of light emitting elements that transmit an optical signal via an optical signal transmission path;
A control circuit that determines whether to turn on or off each light emitting element based on a signal to be transmitted;
The signal intensity of light emitted from each light-emitting element is based on an intensity value that is different from each other and that uniquely determines a plurality of intensity values related to the sum based on the sum of any plurality of intensity values. A drive circuit that emits light from the light-emitting element that is determined to be turned on by the control circuit according to the determined intensity value;
A transmission apparatus comprising: Using a transmission device including a plurality of light emitting elements that transmit an optical signal via an optical signal transmission path,
A step of determining whether each light emitting element is turned on or off based on a signal to be transmitted;
Each of the light emitting elements emits light from a first group that emits light for a half period of the clock signal from a predetermined phase of the clock signal, and light emitted from a point that is shifted by a half period from the predetermined phase of the clock signal. If there is a light emitting element that belongs to the first group and should be lit, the second group emits light for a half period of the clock signal from the predetermined phase of the predetermined clock signal. If there is a light emitting element that should be turned on, the step of emitting light from a point shifted by a half cycle from the predetermined phase of the clock signal, and the step of emitting light by the half cycle of the clock signal;
An optical signal transmission method comprising:

Images