# US 10,371,573 B2 · Electromagnetic power measurement and reporting

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- Number: US 10,371,573 B2
- Document ID: US10371573B2
- Status: Granted
- Kind: B2
- Application number: 14/594,869
- Filed: 2015-01-12
- Published: 2016-07-14
- Granted: 2019-08-06
- Earliest claimed: 2015-01-12
- Assignees: Finisar Corporation
- Applicants: Finisar Corporation
- Inventors: Lucy G. Hosking
- Web page: https://patentgrep.com/patent/US10371573B2

## CPC

- G01J 1/44: Electric circuits {(for command of an exposure part G03B7/02)}
- G01J 1/18: using comparison with a reference electric value
- G01J 1/4257: {applied to monitoring the characteristics of a beam, e.g. laser beam, headlamp beam (monitoring arrangements for lasers in general H01S3/0014)}
- H03G 3/3084: {in receivers or transmitters for electromagnetic waves other than radiowaves, e.g. lightwaves (H03G3/32, H03G3/34 take precedence)}
- G01J 2001/444: {Compensating; Calibrating, e.g. dark current, temperature drift, noise reduction or baseline correction; Adjusting}
- G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N)
- H03G: CONTROL OF AMPLIFICATION

## Abstract

A method to measure and report electromagnetic radiation power includes receiving electromagnetic radiation and generating an electrical signal having a magnitude based on the power of the electromagnetic radiation. An adjustable gain may be applied to the electrical signal to generate an amplified electrical signal that may be sampled to generate a digital sample. The adjustable gain may be controlled based on the value of the digital sample and the digital sample may be associated with a gain value. One or more calibration factors may be selected based on the gain value associated with the digital sample and the selected calibration factor(s) may be used to calculate the power of the electromagnetic radiation.

## Claims

### Claim 1

A method to be performed by a receiver optical subassembly for accurately reporting dynamic electromagnetic-radiation power measurements with high resolution, comprising:
receiving, at a photodiode, a light signal from an optical transmitter, the light signal representative of information;
generating, at the photodiode, an electrical signal based on the received light signal;
amplifying, at an adjustable gain amplifier, the electrical signal based on a magnitude of the electrical signal and a resolution zone of an analog to digital converter;
storing a plurality of gain values corresponding to the amplification of the electrical signal;
generating, at an analog to digital converter, a plurality of digital samples based on the amplified electrical signal,
each digital sample of the plurality of digital samples associated with a gain value of the plurality of the gain values;
selecting, at a power calculation module coupled to the analog to digital converter, one or more calibration factors for each gain value of the plurality of gain values;
calculating, at the power calculation module coupled to the analog to digital converter, the power of the electromagnetic radiation by applying the one or more calibration factors to the plurality of digital samples;
formatting, at a power reporting module, the power in units of Decibel-milliwatts (dBm) utilizing a 16-bit scale that ranges from approximately +128.000 dBm to −128.000 dBm with a resolution of 1/256 dBm per count; and
reporting the formatted power using the 16-bit scale for greater reporting resolution.

### Claim 2 (depends on 1)

The method of claim 1, wherein the one or more calibration factors vary according to a value associated with a gain value of the plurality of gain values.

### Claim 3 (depends on 2)

The method of claim 2, wherein the each gain value of the plurality of gain values is a continuous gain value and the continuous gain value is converted to a digital value.

### Claim 4 (depends on 1)

The method of claim 1, wherein the one or more calibration factors comprises at least one of a slope term and an offset term.

### Claim 5 (depends on 4)

The method of claim 4, wherein the one or more calibration factors comprises an array of slope terms associated with an array of offset terms.

### Claim 6 (depends on 5)

The method of claim 5, wherein the one or more calibration factors comprises an array of eight slope terms associated with an array of eight offset terms.

### Claim 7 (depends on 1)

The method of claim 1, wherein the one or more calibration factors comprises at least one of an exponential function, a polynomial function, or a logarithmic function.

### Claim 8 (depends on 1)

The method of claim 1, wherein the one or more calibration factors are arranged in a look-up table.

### Claim 9 (depends on 1)

The method of claim 1, wherein the power is formatted and reported in units of microwatts.

### Claim 10 (depends on 1)

The method of claim 1, wherein reporting the formatted power comprises using a 16-bit, signed, fixed-point binary number in two's complement format.

### Claim 11 (depends on 1)

The method of claim 1, wherein reporting the formatted power comprises storing the formatted power in a predefined memory location.

### Claim 12 (depends on 1)

The method of claim 1, wherein reporting the formatted power comprises communicating the formatted power through a communication interface.

### Claim 13

An optical fiber communication system for accurately reporting dynamic electromagnetic-radiation power measurements with high resolution, comprising:
a photodiode configured to receive a light signal from an optical transmitter, the light signal representative of information, the photodiode configured to generate an electrical signal based on the received light signal;
an adjustable gain amplifier having a plurality of amplification gain values and configured to amplify the electrical signal to generate an amplified electrical signal based on a selected amplification gain value of the plurality of amplification gain values; an analog-to-digital converter configured to sample the amplified electrical signal and generate a plurality of digital samples; and
a power calculation module communicatively coupled to the analog-to-digital converter, the power calculation module configured to:
select one or more calibration factors for each calculation gain value of a plurality of calculation gain values, each digital sample of the plurality of digital samples associated with a calculation gain value of the plurality of calculation gain values; and
calculate the power of the electromagnetic radiation by applying the selected one or more calibration factors to the plurality of digital samples; and
a power reporting module configured to format the power in units of Decibel-milliwatts (dBm) utilizing a 16-bit scale that ranges from approximately +128.000 dBm to −128.000 dBm with a resolution of 1/256 dBm per count for greater reporting resolution.

### Claim 14 (depends on 13)

The system of claim 13, wherein the one or more calibration factors varies according to a calculation gain value of the plurality of calculation gain values.

### Claim 15 (depends on 13)

The system of claim 13, wherein the one or more calibration factors comprises an array of slope terms associated with an array of offset terms.

### Claim 16 (depends on 15)

The system of claim 15, wherein the one or more calibration factors comprises an array of eight slope terms associated with an array of eight offset terms.

### Claim 17 (depends on 13)

The system of claim 13, wherein the one or more calibration factors comprises at least one of an exponential function, a polynomial function, and a logarithmic function.

### Claim 18 (depends on 13)

The system of claim 13, wherein the one or more calibration factors are arranged in a look up table.

### Claim 19 (depends on 13)

The system of claim 13, further comprising a power reporting module configured to format and report the power in units of microwatts on a scale.

### Claim 20 (depends on 13)

The system of claim 13, further comprising a receiver optical subassembly, wherein each of the adjustable gain amplifier, the analog-to-digital converter, the a power calculation module, and the a power reporting module are included in the receiver optical subassembly.