JPH0290824A - Optical reception circuit - Google Patents

Abstract

PURPOSE:To simplify a circuit constitution and a scale by switching an optical output path in accordance with the input level of light through the use of the optical switching element of current control. CONSTITUTION:An optical fiber 1 is connected to the input-side of the optical switching element 2, and optical receivers 3 and 4, both of which have respectively different gains, are connected to the side of two outputs of the optical switching element 2. Input light is inputted to the optical switching element 2 through the optical fiber 1, and input light is segmented into the optical receivers 3 and 4 since the refractive index of the element 2 changes by a control current Icont. The segment operates to the optical receiver 3-side having the large gain when the optical level is small, and to the optical receiver 4-side having the small gain when the optical level is large. The control current uses that the optical current which occurs by the input optical level of a photodetector 5 flows into a resistance 6 and a resistance 7 and which generates a voltage. Thus, the dynamic ranges of respective receivers in sufficient with 1/2 of a whole system, and a control current circuit does not need a linear operation, whereby the circuit can be obtained by the simple constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical transmission system, and particularly to an optical receiver having a wide dynamic range function.

[Conventional technology]

In order to satisfy the function χ of a wide dynamic range, optical receivers used in conventional optical transmission systems adjust the gain of the amplifier according to the output voltage, as described in "New Edition Optical Fiber Communication", Niki Tsushin Gijutsu Newssha, page 371. An automatic gain control (hereinafter referred to as AGC) method that changes the

[Problem to be solved by the invention]

In the above-mentioned conventional technology, in order to satisfy the dynamic range of light, an electric circuit is used in the optical receiver that receives the light.
Performing GC. In this case, in order to generate the AGC voltage, an output voltage peak value detection circuit and an AGC voltage amplifier are required.

Furthermore, the equivalent amplifier also needs to have a large gain in order to widen the dynamic range, and therefore has a multi-stage amplifier structure. For this reason, the single circuit configuration and scale are complicated and large, which poses a problem in making it cheaper and smaller, more economical, and more commonly used.

An object of the present invention is to secure a wide dynamic range by using only original switching elements without making the configuration of an optical receiving circuit complex.

[Means for solving the problem] The above purpose is to solve the problem by using a switching element for surge control.
This is achieved by switching the optical output path depending on the optical input level. This is because the optical receiving circuit only needs to be set to an amplification degree suitable for each input light level, and the circuit configuration and scale are simpler and smaller than in the conventional system.

[Operation] An optical switching element is provided on the input side of the optical receiver to switch the output path of the input source using a control current from the optical receiver. As a result, the output path is divided according to the input source level, and the dynamic range of the light input to each optical receiver is halved compared to when no switching element is used, so the dynamic range of the optical receiver is The range should be 1/2. In addition, since this control atlL flow only turns the switching element ON and OFF, the current only needs to be turned ON or OFF. For this reason,
The optical receiver circuit configuration is also simpler than the previous AGCfi pressure circuit.

From the above, it is possible to realize an optical receiver with the same dynamic range as the conventional one with a simple circuit configuration.

[Example] An example of the present invention will be described below with reference to the drawings. The original fiber 1 is connected to the input (III) of the original switching element 2. Optical receivers 3 and 4 each having a different gain are connected to the two output sides of the optical switching element 2. A control current is input from the device 3, t to the main switching element 2.In addition, in the optical receiver, as shown in FIG. They are connected in series.The voltage generated across the resistor 7 is converted into a control current by the voltage-current f converter 9 and output.

Next, the operation of this embodiment will be explained. The input source passes through the original fiber 1 and is input to the original switching element 21C. Since the refractive index of this element 2 changes due to the restriction of the current Icontic, the input light should be divided into the optical receiver 3.4. This division operates on the optical receiver 3 side with a large gain when the original level is low, and on the optical receiver 4 side with a small gain when the original level is high. Therefore, the dynamic range of the amplifier 8 in each receiver may be 1/2 of the range of the entire system. Further, the control current utilizes the fact that a charging current generated by the input source level of the receiving FT element 5 flows through the resistors 6 and 7 to generate a voltage. That is, the resistor 7 is set to an appropriate value, and the voltage generated across the resistor 7 is input to the piezo-current converter and used as a current limit for the output current.

However, this cut! Ill change operates at the point of change of this control current.

Based on this, in this embodiment, the optical switching element selects the optical receiver according to the source level, thereby increasing the dynamic range of each receiver by changing the overall system (172).
, This makes it easy to remove the amplifier, and the light receiving element (AP
The multiplication factor of I)) can also be reduced, and noise caused by current can also be reduced. Also, since the control current circuit does not require linear operation in AC) Ct like the pressure circuit, it can be realized with a simple circuit configuration as shown in FIG.

[Efficacy of the Invention iJ:J According to the above-mentioned f-, according to the present invention, in an optical receiver that requires a wide dynamic range, the circuit configuration and scale of each receiver device can be improved. It can be realized easily and with a small size.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of an optical receiver in this embodiment. 1... Original fiber 2... Original switching element 5... Optical receiver (large gain) 4... Optical receiver (gain factor) 5... Photo receiving element (APD) 6... Protective resistor 7... Control voltage adjustment resistor 8...Amplifier 9...Pressure-current converter.

Claims (1)

[Claims] 1. An optical switching element that can switch the output path of an input optical signal using a control current, and the output side of the element has a gain according to the optical level, and also generates a control current that determines the input level, An optical receiving circuit comprising an optical receiver that inputs the optical signal to an optical switching element.