JP2001036469A - Optical transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical transmitter that has a function of preventing in advance deterioration in the reception sensitivity due to a decreased luminous quantity. SOLUTION: The optical transmitter consists of a transmission section T where an optical modulator 3 modulates an output light of a semiconductor laser 1 with a transmission signal of a transmission signal source 2 and outputs a modulated laser beam and of a reception section R where a photo diode 4 of a receiver 7 converts a signal light transmitted through an optical fiber OF, a preamplifier 5 amplifies and outputs an AC signal component included in the modulated laser beam, a notice signal generator 8 detects a voltage V0 (signal light intensity) corresponding to the luminous quantity of the modulated laser beam received by the photo diode 4, a comparator 6 compares the voltage V0 with a reference voltage Vref and the generator 8 generates a notice signal when the detected voltage V0 is the reference voltage Vref or below.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission device using an optical fiber.

[0002]

2. Description of the Related Art In recent years, optical transmission devices using optical fibers have been used for various purposes. When an optical signal is transmitted and received, a fluctuation or a decrease in the light intensity causes a deterioration in the receiving sensitivity or the like, so that it is necessary to monitor the light intensity in the entire system. Conventionally, monitoring of light intensity has been performed by monitoring the output power of a semiconductor laser used as a light source in a transmission unit. However, such monitoring information has a problem that it is not possible to cope with fluctuations and reductions in light intensity due to aging of the semiconductor laser and other factors.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and generates an annunciation signal when the intensity of a received optical signal falls below a predetermined reference value.
It is an object of the present invention to provide an optical transmission device having a function of preventing reception sensitivity deterioration due to a decrease in light amount.

[0004]

An optical transmission device according to the present invention comprises:
A receiver for receiving the signal light transmitted through the optical fiber, and comparing the intensity of the received signal light with a predetermined reference value to generate a notification signal when the intensity of the signal light becomes equal to or less than the reference value And means. With this configuration, it becomes possible for the optical transmission device to prevent the deterioration of the receiving sensitivity due to the decrease in the amount of light.

[0005]

FIG. 1 shows the configuration of an optical transmission device according to one embodiment of the present invention. In FIG. 1, in the optical transmission device, a transmission unit T and a reception unit R are connected by an optical fiber OF. The transmission unit T includes a semiconductor laser 1 and an optical modulator 3 that modulates output light of the semiconductor laser 1 with a transmission signal from a transmission signal source 2. The receiver R converts the signal light into an electric signal and amplifies the signal light. The receiver 7 compares the intensity of the received signal light with a predetermined reference value to notify when the intensity of the signal light becomes lower than the reference value. And a notification signal generator 8 for generating a signal.

[0006] The receiver 7 receives an optical fiber O from the transmitting section T.
A photodiode 4 for receiving the modulated laser light transmitted through F, a load resistor R0 connected between the anode of the photodiode 4 and the ground, a preamplifier 5, and a connection between the photodiode 4 and the load resistor R0. A capacitor C0 connecting the point to the input terminal of the preamplifier 5, a capacitor C1 connected in series between the output terminal of the preamplifier 5 and the output terminal Vout, a resistor R1, and a connection point of the capacitor C1 and the resistor R1. And a resistor R2 connected between the ground and the ground. Further, the notification signal generator 8 includes the photodiode 4
Resistors R3 and R4 connected in series between the connection point of the load resistor R0 and the ground, a detection voltage V0 and a reference voltage Vre corresponding to the amount of received light detected at the connection point of the resistors R3 and R4.
and a comparator 6 that generates an alarm signal when the detected voltage V0 is equal to or lower than the reference voltage Vref.

In the optical transmission device having the above configuration, the transmitting section T
Inputs the output light of the semiconductor laser 1 to the optical modulator 3, modulates the output light of the semiconductor laser 1 with the transmission signal from the transmission signal source 2 by the optical modulator 3, and modulates the modulated laser light via the optical fiber OF. The data is transmitted to the receiving unit R. The receiving unit R converts the transmitted modulated laser light into a photocurrent by the photodiode 4, supplies an AC signal component included in the modulated laser light to the preamplifier 5 through the capacitor C0, and amplifies the signal by the preamplifier 5. , And to a subsequent circuit (not shown) via the capacitor C1.

On the other hand, the notification signal generator 8 detects a voltage V0 (signal light intensity) corresponding to the amount of modulated laser light input to the photodiode 4 at a connection point between the resistors R3 and R4, and detects this at a comparator. 6 and compared with the reference voltage Vref,
When the detection voltage V0 is equal to or lower than the reference voltage Vref, a notification signal output is generated.

[0009]

As described above, the optical transmission apparatus according to the present embodiment detects the intensity of the received signal light, and generates an annunciation signal when the intensity of the signal light becomes equal to or less than the reference value. It is possible to prevent the reception sensitivity from deteriorating due to the decrease in the light power.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an optical transmission device according to an embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 semiconductor laser 2 transmission signal source 3 optical modulator 4 photodiode 5 preamplifier 6 comparator

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyuki Takato 465 Osato-cho, Kofu City, Yamanashi Prefecture Pioneer Video Co., Ltd. F term (reference) 5K002 AA03 EA06 FA01 5K042 CA10 DA11 EA03 FA25 GA01 HA13 JA01

Claims (1)

[Claims] A receiver for receiving the signal light transmitted via the optical fiber; and comparing the intensity of the received signal light with a predetermined reference value so that the intensity of the signal light becomes equal to or less than the reference value. Means for generating a notification signal when the signal is transmitted.