JPH06318928A - Optical wavelength multiplex transmission system using light emitting element and light receiving element with multiple wavelengths - Google Patents

Abstract

PURPOSE:To provide the optical wavelength multiplex transmission line, which is low-priced and is immune to vibrations, unnecessitating a synthesizer and a branching filter by using a light emitting element and a light receiving element with multiple wavelengths. CONSTITUTION:At a transmission part, an LED1 4 and an LED2 5 built in an LED 3 and provided with different center light emitting wavelengths are modulated by two different signals, and signal beams are simultaneously sent to one optical fiber 7. At a reception part, the signal beams are received by a PD1 10 and a PD2 11 built in a color sensor 9 and provided with different center sensitivity wavelengths, and a target signal is separately provided by subtracting the output signal and a signal passed through an attenuator or amplifiers 14 and 15 each other by using subtracters 16 and 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION A signal processing system according to the present invention and a transmission device having the function thereof provide an inexpensive optical wavelength multiplexing transmission line which does not require a multiplexer and a demultiplexer. Therefore,
It can be used in the field of simultaneous transmission of multiple signals in processing equipment, inspection equipment and transportation equipment in factories.

[0002]

2. Description of the Related Art Conventionally, in a multiplex transmission system using lights of different wavelengths, on the transmitting side, individual light emitting elements having different light emitting wavelengths are used for electrical-optical conversion, and then a multiplexer is used to generate one optical signal. Sends an optical signal to the fiber. Further, on the receiving side, optical signals having different wavelengths are separated by a demultiplexer, and light-to-electric conversion is performed by a light receiving element having sensitivity to each wavelength to simultaneously acquire a plurality of desired signals.

[0003]

In the conventional optical wavelength division multiplex transmission system, a multiplexer and a demultiplexer are indispensable, and many optical connectors are required accordingly. As a result, there have been problems such as an increase in cost and weight, and a decrease in reliability due to an increase in precision optical coupling portions.

[0004]

DISCLOSURE OF THE INVENTION The present invention is a multicolor emission LE.
By using a multi-wavelength light emitting element such as D and a multi-wavelength light receiving element such as a color sensor in a multiplex transmission device, a multiplexer and a demultiplexer are not required, and the other problems described above are solved.

If the spectral sensitivity characteristics of the plurality of light receiving elements on the receiving side are separated from each other on the wavelength axis with respect to the plurality of emission wavelengths on the transmitting side, no problem occurs in signal transmission. However, in general, the spectral sensitivity characteristics of the light-receiving elements built into color sensors, etc., have a wide spectrum distribution, so there is overlap, and so-called reception crosstalk occurs, which detects different signal lights. .

Therefore, a method of removing this crosstalk on the receiving side will be described with reference to drawings and mathematical formulas by taking a two-color light emitting LED and a color sensor as an example. In FIG. 1, two LED elements built into the two-color light emitting LED 3, LED ₁
4 and the emission intensity characteristic function of LED ₂ 5 _{e 1} (λ) and _{e 2}
(Λ), p ₁ is the spectral sensitivity characteristic function of the photodiodes PD ₁ 10 and PD ₂ 11 built in the color sensor 9.
Let (λ) and p ₂ (λ).

First, the output of PD ₁ 10 when receiving only one signal light e ₁ (λ) is two functions e
_{It is} a value obtained by integrating the product of ₁ (λ) and p ₁ (λ) over the wavelength region. Now, this is represented as P ₁ (e ₁ ), and hereinafter, similarly, P ₁ (e ₂ ), P ₂ (e ₁ ), and P ₂ (e ₂ ).

The output P ₁ of PD ₁ 10 and the output P of PD ₂ 11 when e ₁ (λ) and e ₂ (λ) are simultaneously received
₂ is simple, if the external amplification factor after receiving light is 1,

[0009]

[Equation 1]

[0010]

[Equation 2] It can be expressed as. Here, P ₂ (e ₁ ) / P ₁ (e
₁ ) and P ₁ (e ₂ ) / P ₂ (e ₂ ) are LED ₁₃ and LE
Since it is a constant determined by the individual characteristics of D ₂ 4, PD ₁ 10, and PD ₂ 11,

[0011]

[Equation 3]

[0012]

[Equation 4] And substituting these into Equation 1 and Equation 2,

[0013]

[Equation 5]

[0014]

[Equation 6] The relationship is established. Therefore, from Equation 5 and Equation 6,

[0015]

[Equation 7]

[0016]

[Equation 8] Becomes

Equations 7 and 8 are simultaneously applied to the color sensor 9 in which the two signal lights e ₁ (λ) and e ₂ (λ) of the LED 3 have the spectral sensitivity characteristics of p ₁ (λ) and p ₂ (λ). Even if the light enters
If K ₁ and _{K 2} are known, the respective outputs _P 1, _{P 2} than _{e 1} signal _P 1 contained in the (lambda) _{(e 1)} and the signal _P 2 included in the _{e 2 (λ) (e 2} ) It shows that it can be derived. The relative sensitivity ratio K ₁ is equal to PD ₁ 10 and PD when the signal light e ₁ (λ) of the LED ₁₄ is incident on the color sensor 9.
_Since it is the output ratio of ₂ 11 and K ₂ is the output ratio of PD ₁ 10 and PD ₂ 11 when only the signal light e ₂ (λ) is incident, it can be measured experimentally.

[0018]

By applying the above reception crosstalk removing means, a multicolor light emitting LED which is generally commercially available
By using a multi-wavelength light emitting element such as and a multi-wavelength light receiving element such as a color sensor, it is possible to realize an optical wavelength multiplex transmission device that does not require a multiplexer and a demultiplexer.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION With the configuration of FIG. 1, two wavelengths of light, each of which is separately intensity-modulated by different analog signals of two channels, are transmitted even after passing through a transmission / reception system coupled by a single optical fiber. It has been confirmed that can be separated and output practically without any problem. Similarly, the flow of signals will be described with reference to FIG.

First, in the transmission section, two different signals Vi1 and Vi2 are supplied to the LE and LE converters by the different voltage-current converters 1 and 2, respectively.
LED ₁₄ with different center emission wavelengths built in D3
And it is converted to a drive current of the LED ₂ 5. Next, LED3
Is optically connected to one optical fiber 7 by an optical connector 6, and signal lights of two wavelengths are simultaneously sent out.

In the receiving section, the signal light is received by the color sensor 9 through the optical connector 8, and the outputs of the PD ₁ 10 and PD ₂ 11 having different central sensitivity wavelengths are output by the current-voltage converters 12, 13. Convert to voltage. Next, an attenuator 1 for attenuating the voltage according to the values of relative sensitivity ratios K ₁ and K _2.
Pass through 4 and 15. Finally, each current-voltage converter 1
Attenuator 14 with a different channel than the output from 2, 13
The outputs from 15 are subtracted from each other by subtracters 16 and 17 to obtain target signals Vo1 and Vo2 separately.

When either of the relative sensitivity ratios K ₁ and K ₂ is larger than 1, the attenuator 14 or 15 shown in FIG. 1 is replaced with an amplifier. However, both K ₁ and K ₂ are never greater than 1. Further, in order to effectively remove the crosstalk, it is necessary that the time constant of the electronic circuit of the PD 1 ₁₀ and PD 2 ₁₁ or each stage being built in color sensor 9 identical between the channels.

[0023]

The signal processing system and the transmission device having the function according to the present invention do not require a multiplexer and a demultiplexer which have been indispensable in the past, and provide an optical wavelength multiplex transmission line which is inexpensive and resistant to vibration. . Therefore, it is effective in the field where it is attempted to simultaneously transmit a plurality of signals in processing equipment such as a factory, inspection equipment, and transportation equipment.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of an optical wavelength division multiplexing transmission apparatus according to the present invention.

[Explanation of symbols]

1, 2 Voltage / current converter 3 Two-color light emitting LED 4 Two-color light emitting LED built-in LED (LE
D ₁ ) 5 LED built in two-color LED (LE
D ₂ ) 6, 8 Optical connector 7 Optical fiber 9 Color sensor 10 Photodiode (PD ₁ ) 11 incorporated in color sensor 11 Photodiode (PD ₂ ) 12 13 incorporated in color sensor Current-voltage converter 14 , 15 Attenuators or amplifiers 16, 17 Subtractors

Claims (2)

[Claims] 1. A signal processing method for subtracting one signal from another signal at a certain fixed ratio in order to remove reception crosstalk caused by overlapping of spectral sensitivity characteristics of a multi-wavelength light receiving element over a wavelength distribution. 2. A multicolor emission L having the signal processing function.
An optical wavelength division multiplexing transmission device using a multi-wavelength light emitting element such as an ED and a multi-wavelength light receiving element such as a color sensor.