# US 9,435,712 B2 · OTDR signal injection for multi-band optical power balancing

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- Number: US 9,435,712 B2
- Document ID: US9435712B2
- Status: Granted
- Kind: B2
- Application number: 14/583,950
- Filed: 2014-12-29
- Published: 2016-06-30
- Granted: 2016-09-06
- Earliest claimed: 2014-12-29
- Assignees: Verizon Patent and Licensing Inc.
- Applicants: Verizon Patent and Licensing Inc.
- Inventors: David Z. Chen; Wenjia Wang
- Web page: https://patentgrep.com/patent/US9435712B2

## CPC

- G01M 11/3127: {using multiple or wavelength variable input source}
- G01M 11/3109: {Reflectometers detecting the back-scattered light in the time-domain, e.g. OTDR}
- G01M 11/3181: {Reflectometers dealing with polarisation}
- H04B 10/071: using a reflected signal, e.g. using optical time domain reflectometers [OTDR]
- H04B 10/07955: {Monitoring or measuring power}
- H04J 14/0221: {Power control, e.g. to keep the total optical power constant}
- H04J 14/0282: {WDM tree architectures}
- H04J 14/06: Polarisation multiplex systems
- H04Q 2011/0079: {Operation or maintenance aspects}
- G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- H04B: TRANSMISSION
- H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S)
- H04Q: SELECTING (switches, relays, selectors H01H; wireless communication networks H04W)

## Abstract

A system includes an Optical Time Domain Reflectometer (OTDR) that injects a first OTDR signal at a first optical wavelength, a first power level and a first polarization state into an optical fiber. The system further includes an OTDR monitor that monitors multi-band optical signals on the optical fiber, selects a second power level and a second polarization state based on the monitoring of the multi-band optical signals, and determines parameters associated with the optical fiber based on the monitoring. The OTDR injects a second OTDR signal at the first optical wavelength, the selected second power level and the selected second polarization state into the optical fiber. The system operates to allow un-balanced power levels across multiple wavelength bands to be balanced due to inter-channel Raman power shift.

## Claims

### Claim 1

A method, comprising:
injecting, from at least one Optical Time Domain Reflectometer (OTDR), one or more first OTDR signals at one or more first optical wavelengths into an optical fiber;
monitoring multi-band optical signals, including reflected OTDR signals corresponding to the first OTDR signals, on the optical fiber;
determining parameters associated with the optical fiber based on the first OTDR signals and the monitoring;
adjusting, at the at least one OTDR, a power level and a polarization state of one or more second OTDR signals at one or more second optical wavelengths based on the monitoring until power levels associated with the multi-band optical signals are balanced; and
injecting, from the at least one OTDR, the one or more second OTDR signals at the one or more second optical wavelengths into the optical fiber.

### Claim 2 (depends on 1)

The method of claim 1, wherein the determined parameters comprise a fiber length, an overall attenuation and/or an optical return loss of the optical fiber.

### Claim 3 (depends on 1)

The method of claim 1, wherein adjusting the power level and the polarization state comprises:
iteratively adjusting, at the at least one OTDR, the power level and the polarization state of the one or more second OTDR signals based on the monitoring until the power levels associated with the multi-band optical signals are balanced.

### Claim 4 (depends on 1)

The method of claim 1, wherein the one or more first optical wavelengths are the same optical wavelengths as the one or more second optical wavelengths.

### Claim 5 (depends on 1)

The method of claim 1, wherein the one or more first optical wavelengths are different optical wavelengths than the one or more second optical wavelengths.

### Claim 6

A system, comprising:
a first Optical Time Domain Reflectometer (OTDR) configured to inject a first OTDR signal at a first optical wavelength, a first power level and a first polarization state into an optical fiber,
an OTDR monitor configured to:
monitor multi-band optical signals, including a reflected OTDR signal corresponding to the first OTDR signal, on the optical fiber, and
select a second power level and a second polarization state based on the monitoring of the multi-band optical signals,
determine parameters associated with the optical fiber based on the monitoring, and
wherein the first OTDR is further configured to inject a second OTDR signal at the first optical wavelength, the selected second power level and the selected second polarization state into the optical fiber to balance power levels associated with the multi-band optical signals.

### Claim 7 (depends on 6)

The system of claim 6, wherein the OTDR monitor is further configured to:
select a third power level and a third polarization based on the monitoring of the multi-band optical signals subsequent to injecting the second OTDR signal,
wherein the first OTDR is further configured to inject a third OTDR signal at the first optical wavelength, the third power level and the third polarization into the optical fiber to further balance the power levels associated with the multi-band optical signals.

### Claim 8 (depends on 7)

The system of claim 7, wherein third power level is different than the second power level.

### Claim 9 (depends on 7)

The system of claim 7, wherein the third polarization is different than the second polarization.

### Claim 10 (depends on 6)

The system of claim 6, wherein the second power level is different than the first power level.

### Claim 11 (depends on 6)

The system of claim 6, wherein the second polarization is different than the first polarization.

### Claim 12 (depends on 6)

The system of claim 6, further comprising:
a second OTDR configured to inject a third OTDR signal at a second optical wavelength, a third power level and a third polarization into the optical fiber, wherein the second OTDR is configured to inject the third OTDR signal simultaneously with the first OTDR injecting the first OTDR signal; and
wherein the OTDR monitor is further configured to:
select a fourth power level and a fourth polarization based on the monitoring of the multi-band optical signals,
wherein the second OTDR is further configured to inject a fourth OTDR signal at the second optical wavelength, the fourth power level and the fourth polarization into the optical fiber.

### Claim 13

A non-transitory computer-readable medium containing instructions executable by at least one processor, the computer-readable medium comprising:
one or more instructions for causing a first Optical Time Domain Reflectometer (OTDR) to inject one or more first OTDR signals into an optical fiber, wherein the one or more first OTDR signals have a first optical wavelength, a first power level, and a first polarization state;
one or more instructions for monitoring multi-band optical signals, including reflected OTDR signals corresponding to the first OTDR signals, on the optical fiber; and
one or more instructions for causing the first OTDR to inject one or more second OTDR signals into the optical fiber, based on the monitoring of the multi-band optical signals, to balance power levels associated with the multi-band optical signals, wherein the one or more second OTDR signals have a second optical wavelength, a second power level and a second polarization state.

### Claim 14 (depends on 13)

The non-transitory computer-readable medium of claim 13, wherein the second optical wavelength is a same wavelength as the first optical wavelength.

### Claim 15 (depends on 13)

The non-transitory computer-readable medium of claim 13, wherein the second power level is different than the first power level and the second polarization state is the same as the first polarization state.

### Claim 16 (depends on 13)

The non-transitory computer-readable medium of claim 13, wherein the second power level is the same as the first power level and the second polarization state is different than the first polarization state.

### Claim 17 (depends on 13)

The non-transitory computer-readable medium of claim 13, further comprising:
one or more instructions for determining parameters associated with the optical fiber based on the one or more first or second OTDR signals and based on the monitoring of the multi-band optical signals on the optical fiber.

### Claim 18 (depends on 13)

The non-transitory computer-readable medium of claim 13, wherein the one or more instructions for monitoring the multi-band optical signals on the optical fiber comprise:
one or more instructions for monitoring power levels associated with the multi-band optical signals on the optical fiber.

### Claim 19 (depends on 18)

The non-transitory computer-readable medium of claim 18, further comprising:
one or more instructions for determining the power levels, at specific wavelengths throughout multiple bands in which the multi-band optical signals have been transmitted;
one or more instructions for determining whether the determined power levels are balanced across the multiple bands.

### Claim 20 (depends on 19)

The non-transitory computer-readable medium of claim 19, wherein the one or more instructions for causing the first OTDR to inject one or more second OTDR signals into the optical fiber further comprises:
one or more instructions for setting the second power level different than the first power level, or the second polarization state different than the first polarization state, if the determined power levels are not balanced across the multiple bands.