# US 5,347,385 A · Frequency-multiplex optical transmission apparatus

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- Number: US 5,347,385 A
- Document ID: US5347385A
- Status: Granted
- Kind: A
- Application number: 07/830,317
- Filed: 1992-01-31
- Granted: 1994-09-13
- Earliest claimed: 1991-02-08
- Assignees: Sumitomo Electric Industries, Ltd.
- Inventors: Mitsutoshi Imada
- Web page: https://patentgrep.com/patent/US5347385A

## CPC

- H04B 10/50: Transmitters
- H01S 5/06213: {Amplitude modulation}
- H04B 10/504: {using direct modulation}
- H04B 10/564: Power control
- H01S 5/06808: {by monitoring the electrical laser parameters, e.g. voltage or current}
- H01S 5/06825: {Protecting the laser, e.g. during switch-on/off, detection of malfunctioning or degradation}
- H01S 5/0683: by monitoring the optical output parameters
- H01S 5/06832: {Stabilising during amplitude modulation}
- H04B: TRANSMISSION
- H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL

## Abstract

A frequency-multiplex optical transmission apparatus for carrying out frequency-multiplex optical transmission by supplying an analog-frequency-multiplexed RF input signal to a laser diode. In the apparatus, part of the RF input signal taken out by a splitter is detected by a power detector. In response to an output signal of the power detector, an indicator driver causes an indicator to indicate a modulation signal level for the laser diode. The level of the RF input signal is adjustable by an attenuator while observing the indication state of the indicator.

## Claims

### Claim 1

An apparatus for carrying out frequency-multiplex optical transmissions, comprising:
means for supplying an analog-frequency-multiplexed RF input signal to a laser diode;
split means for taking out part of the RF input signal before being supplied to said laser diode;
detection means for detecting the RF input signal obtained from the split means;
an indicator; and
drive means for causing the indicator to indicate a modulation signal level of the laser diode on the basis of a modulation signal level of said RF input signal obtained from an output signal of the detection means.

### Claim 2 (depends on 1)

The apparatus according to claim 1, further comprising level adjustment means for adjusting a level of the RF input signal prior to the taking out operation of said split means.

### Claim 3 (depends on 2)

The apparatus according to claim 2, wherein the level adjustment means includes an attenuator.

### Claim 4 (depends on 1)

The apparatus according to claim 1, wherein the split means includes a split transformer.

### Claim 5 (depends on 1)

The apparatus according to claim 1, wherein the detection means includes an RF power detector.

### Claim 6 (depends on 5)

The apparatus according to claim 5, wherein the RF power detector consists of a diode, a resistor, and a capacitor.

### Claim 7 (depends on 1)

The apparatus according to claim 1, wherein the indicator includes a plurality of light emitting diodes, and said drive means causes a designated one of the light emitting diodes to light when the modulation signal level to the laser diode is an optimum value based on the output signal.

### Claim 8 (depends on 7)

The apparatus according to claim 7, wherein the driving means causes light emitting diodes other than the designated light emitting diode to light when the modulation signal level to the laser diode is not an optimum value based on the output signal.

### Claim 9 (depends on 1)

The apparatus according to claim 1, wherein indicator includes a single light emitting diode, and said drive means causes said single light emitting diode to light when the modulation signal level to the laser diode is an optimum value based on the output signal.

### Claim 10 (depends on 1)

The apparatus according to claim 1, wherein the indicator includes a plurality of light emitting diodes, each diode corresponding to a different level of signal modulation.

### Claim 11 (depends on 10)

The apparatus according to claim 10, wherein the driving means drives the light emitting diodes to indicate optimum modulation, deep modulation, and shallow modulation based on the output signal.

### Claim 12 (depends on 1)

The apparatus according to claim 1, wherein the indicator includes a plurality of light emitting diodes, the plurality of light emitting diodes include a centrally positioned light emitting diode and at least one light emitting diode positioned on a first and second side of the centrally positioned light emitting diode.

### Claim 13 (depends on 12)

The apparatus of claim 12, wherein the drive means causes the centrally positioned light emitting diode to light when the modulation signal level is an optimum value based on the output signal.

### Claim 14 (depends on 13)

The apparatus of claim 13, wherein the driving means causes the light emitting diode positioned on a first side of the centrally positioned diode to light when the modulation signal level is lower than the optimum value, and the light emitting diode positioned on the second side of the centrally positioned diode to light when the modulation signal level is higher than the value optimum based on the output signal.