JPH10107738A - Optical receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extend a range of a light receiving level of an optical signal and to reduce the power consumption. SOLUTION: The receiver is provided with a light receiving element 1, a monitor circuit 2 monitoring an optical signal received by the light receiving element 1, two stages of amplifier circuits 3 or over that amplify an electric signal outputted from the light receiving element 1, and a gain adjustment circuit 4 making a signal level of the electric signal stable. In this case, a gain of the 1st stage amplifier circuit 3 is variably controlled by using an output voltage of the monitor circuit 2. Furthermore, the 1st stage amplifier circuit 3 is provided with a through-circuit 5, a gain adjustment amplifier circuit 6 and a changeover device 7 to select either of both the circuits 5, 6 and when a level of an optical signal made incident onto the light receiving element 1 is a prescribed level or over, the signal received by the 1st stage amplifier circuit 3 is given to the through-circuit 5 and when a level of the optical signal made incident onto the light receiving element 1 is a prescribed level or below, the signal received by the 1st stage amplifier circuit 3 is given to the gain adjustment amplifier circuit 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical receiver used in a CATV system and other optical communication systems.

[0002]

2. Description of the Related Art An optical receiver generally has a circuit configuration as shown in FIG. 3, and includes a light receiving element A, two or more amplifier circuits B connected in cascade, and a gain adjustment circuit C. The first-stage amplifier circuit B plays the role of a preamplifier for the second and subsequent amplifier circuits B. In this optical receiver, an input optical signal is converted into an electric signal by a light receiving element A, and the electric signal A is amplified by a first-stage amplifier circuit B, and then is amplified by a gain adjustment circuit C in accordance with the level of the signal. The level is stabilized by being attenuated. Specifically, when the level of the electric signal is large, the attenuation is large, and when the level is small, the attenuation is small. This stabilized electric signal is amplified to a predetermined level by the amplifier circuits B of the second and subsequent stages and becomes an external output.

[0003]

The gain of the first-stage amplifier circuit B of the optical receiver shown in FIG. 3 is fixed, and functions effectively for an electric signal having a level within a predetermined range. That is, within the specified range, the minimum level required for the gain adjustment circuit C and the amplification circuit B at the subsequent stage is created for a low-level signal, and the distortion characteristic is obtained for a high-level signal. Is amplified to such an extent that the deterioration of the element falls within an allowable range. However, a signal of a low level below a predetermined range or a signal of a high level above the same range does not function effectively due to insufficient amplification factor, deterioration of distortion characteristics, and the like. That is, there is a problem that the range for the input level of the optical signal is narrow. For large-level signals within the specified range,
Although a large distortion does not occur, a signal that would otherwise be sufficient only by the latter-stage amplifier circuit D is amplified by the first-stage amplifier circuit A, so that wasteful power is consumed. Have a problem.

An object of the present invention is to provide an optical receiver having a wide dynamic range and capable of saving power.

[0005]

As shown in FIG. 1, the optical receiver according to the first aspect of the present invention includes a light receiving element 1 for receiving an optical signal and converting it into an electric signal. A monitor circuit 2 capable of monitoring an optical signal to be transmitted, an amplifier circuit 3 for amplifying an electric signal output from the light receiving element 1, two or more stages, and a gain adjusting circuit 4 for stabilizing the signal level of the electric signal.
In the optical receiver provided with the above, the gain of the first-stage amplifier circuit 3 can be variably controlled using the output voltage of the monitor circuit 2.

In the optical receiver according to the second aspect of the present invention, as shown in FIG. 2, a through circuit 5, a gain adjustment amplifier circuit 6, and a switch for switching between the two circuits 5, 6 are provided in the first stage amplifier circuit 3. 7, the signal input to the first-stage amplifier circuit 3 is passed through the through circuit 5 when the optical signal level incident on the light receiving element 1 is equal to or higher than a predetermined value, and is passed to the gain adjustment amplifier circuit 6 when the optical signal level is equal to or lower than the predetermined value. It is made to pass.

[0007]

Embodiment 1 An embodiment of an optical receiver according to the present invention will be described with reference to FIG. The optical receiver includes a light receiving element 1 for receiving an optical signal and converting the light signal into an electric signal;
A monitor circuit 2 for monitoring an optical signal (the level of the optical signal) received by the amplifier, an amplifier circuit 3 of two or more stages for amplifying an electric signal output from the light receiving element 1, and an amplifier circuit 3 for the first and second stages. And a gain adjustment circuit 4 provided between them for stabilizing the level of the electric signal.

The light receiving element 1, the monitor circuit 2, the second and subsequent stages of the amplifier circuit 3, and the gain adjustment circuit 4 can all be the same as those used in conventional optical receivers. For example, the same one as shown in FIG. 3 can be used. Although a monitor circuit is not shown in FIG. 3, it is provided as standard. The monitor circuit 2 outputs a voltage corresponding to the light receiving level of the light receiving element 1, and outputs a low voltage when the light receiving level is low, and outputs a high voltage when the light receiving level is high.

The first-stage amplifier circuit 3 is of a variable gain type instead of the fixed gain type, and the amplification gain can be varied by an external control voltage.
In this case, the output voltage output from the monitor circuit 2 is input as the control voltage of the first-stage amplifier circuit 3, and the gain changes in accordance with the light receiving level of the optical signal in the light receiving element 1. Specifically, the gain is reduced as the light receiving level increases, and the gain is increased as the light receiving level decreases.

In the optical receiver described above, since the gain of the first-stage amplifier circuit 3 is appropriately adjusted according to the light receiving level of the optical signal, generation of noise due to insufficient gain and generation of distortion due to excessive gain are suppressed over a wide range. Thus, the allowable light receiving level is expanded. Further, when the light receiving level is high, the gain of the first-stage amplifier circuit 3 is adjusted to be low, so that the power consumption of the first-stage amplifier circuit 3 is suppressed, and wasteful power consumption is suppressed as a whole.

[0011]

Embodiment 2 FIG. 2 shows another embodiment of the optical receiver according to the present invention. In this example, the first-stage amplifier circuit 3 in the first embodiment is composed of a first amplifier circuit 8, a subsequent second amplifier circuit (amplifier circuit for gain adjustment) 6, and a through circuit 5, and the second amplifier circuit 6 And the through circuit 5 are configured such that either one of them is selected by the switchers 7 at both ends thereof. The switching of the switch 7 is performed by a comparison circuit 9 provided in the monitor circuit 2 of the light receiving element 1.

The comparison circuit 9 monitors the level of the light signal received by the light receiving element 1 through the monitor circuit 2. The light reception level of the light signal is determined based on a predetermined reference value set in the comparison circuit 9. Is larger or smaller than the appropriate value. This comparison circuit 9
If it is determined that the light reception level exceeds the predetermined value,
The contact of the switch 7 is switched to the through circuit 5 side, and the through circuit 5 is set as a circuit following the first amplifier circuit 8. If it is determined that the light receiving level is lower than a predetermined value, the contact of the switch 7 is changed. Switching to the second amplifier circuit 6 side, the second amplifier circuit 6 is set as a circuit following the first amplifier circuit 8.

In the first-stage amplifier circuit 3, the first amplifier circuit 8 is always operated, and a drive current is always supplied. However, the second amplifier circuit 6 is provided with a switch 7 Thus, the drive current is supplied only when selected, and unnecessary drive current is not consumed.

The gain of each of the first and second amplifier circuits 8 and 6 is fixed, and the first and second amplifier circuits 8 and 6 operate together for a small signal, so that the desired Gain is achieved. In other words, each of the first and second amplifying circuits 8 and 6 has a small gain, so that when a large signal is input, only the first amplifying circuit 8 having a small gain operates to prevent the distortion characteristic from deteriorating. It is.

In the optical receiver described above, the gain of the first-stage amplifier circuit 3 is adjusted in two steps, and cannot be adjusted more finely than the continuously changing signal of the first embodiment. In addition, since the through circuit 5 is selected, deterioration of the distortion characteristics due to the amplifier circuit 3 is prevented, and efficient power saving can be achieved.

[0016]

According to the optical receiver of the present invention, the following effects can be obtained. 1. Distortion characteristics are improved with respect to large-level signals while having a wide dynamic range that can handle small-level signals and large-level signals. 2. Useless power consumption in the first-stage amplifier circuit is eliminated, and power consumption is reduced. 3. The amount of gain adjustment on the side of the subsequent-stage amplifier circuit can be reduced, the deterioration of frequency characteristics is small, and the circuit configuration is simplified.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an optical receiver according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a second embodiment of the optical receiver according to the present invention.

FIG. 3 is a block diagram showing an example of a conventional optical receiver.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light receiving element 2 monitor circuit 3 amplifier circuit 4 gain adjustment circuit 5 through circuit 6 gain adjustment amplifier circuit 7 switch

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04B 10/08

Claims (2)

[Claims] A light receiving element (1) for receiving an optical signal and converting it into an electric signal, a monitor circuit (2) capable of monitoring an optical signal received by the light receiving element (1), and a light receiving element (1). In an optical receiver including two or more stages of an amplifier circuit (3) for amplifying an output electric signal and a gain adjustment circuit (4) for stabilizing the signal level of the electric signal, the output of the monitor circuit (2) is provided. An optical receiver characterized in that the gain of a first-stage amplifier circuit (3) can be variably controlled by using a voltage. 2. The first stage amplifier circuit (3) is provided with a through circuit (5), a gain adjustment amplifier circuit (6), and a switch (7) for switching between the two circuits (5) and (6). When the level of the optical signal incident on the element (1) is equal to or higher than a predetermined value, the signal input to the first-stage amplifier circuit (3) is passed through the through circuit (5). The optical receiver according to claim 1, wherein the optical receiver is configured to pass through (6).