# US 11,309,969 B2 · Fiber communication systems and methods

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- Number: US 11,309,969 B2
- Document ID: US11309969B2
- Status: Granted
- Kind: B2
- Application number: 17/169,600
- Filed: 2021-02-08
- Published: 2021-06-03
- Granted: 2022-04-19
- Earliest claimed: 2016-04-12
- Assignees: Cable Television Laboratories, Inc.
- Applicants: Cable Television Laboratories, Inc.
- Inventors: Zhensheng Jia; Luis Alberto Campos; Curtis Dean Knittle
- Web page: https://patentgrep.com/patent/US11309969B2

## CPC

- H04B 10/504: {using direct modulation}
- H04B 10/502: {LED transmitters}
- H04B 10/505: {using external modulation}
- H04B 10/506: {Multiwavelength transmitters}
- H04B 10/532: Polarisation modulation
- H04B 10/63: Homodyne {, i.e. coherent receivers where the local oscillator is locked in frequency and phase to the carrier signal}
- H04B 10/64: Heterodyne {, i.e. coherent receivers where, after the opto-electronic conversion, an electrical signal at an intermediate frequency [IF] is obtained}
- H04J 14/0305: {in end terminals}
- H04J 14/06: Polarisation multiplex systems
- 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)

## Abstract

An injection locked transmitter for an optical communication network includes a primary seed laser source input substantially confined to a single longitudinal mode, an input data stream, and a laser injected modulator including at least one secondary laser having a resonator frequency that is injection locked to a frequency of the single longitudinal mode of the primary seed laser source. The laser injected modulator is configured to receive the primary seed laser source input and the input data stream, and output a laser modulated data stream.

## Claims

### Claim 1

A transceiver for an optical communication network, comprising:
an input portion configured to receive an input laser signal from a remote primary laser source of the optical communication network, the input laser signal including a coherent tone pair having (i) a first coherent tone containing a downstream modulated signal, and (ii) a second coherent tone containing a downstream unmodulated signal; and
a laser injected modulator including a first secondary laser injection locked to a primary frequency of a single longitudinal mode of the remote primary laser source,
wherein a frequency of the second coherent tone is held constant to a frequency of the first coherent tone, and
wherein the laser injected modulator is configured to receive the downstream unmodulated signal on the second coherent tone, and output an upstream modulated laser signal.

### Claim 2 (depends on 1)

The transceiver of claim 1, wherein the laser injected modulator is configured to implement direct modulation.

### Claim 3 (depends on 1)

The transceiver of claim 1, wherein the laser injected modulator is configured to implement external modulation.

### Claim 4 (depends on 1)

The transceiver of claim 1, wherein the first secondary laser comprises at least one of an LED, a Fabry Perot laser diode, and a vertical-cavity surface-emitting laser.

### Claim 5 (depends on 1)

The transceiver of claim 1, further comprising a first optical circulator in communication with the laser injected modulator and the unmodulated signal on the second coherent tone.

### Claim 6 (depends on 5)

The transceiver of claim 5, wherein the laser injected modulator is configured to implement one of polarization division multiplexing, space division multiplexing, and mode division multiplexing.

### Claim 7 (depends on 6)

The transceiver of claim 6, wherein the laser injected modulator is configured to multiplex the input laser signal at one of an orthogonal polarization, a 60 degree polarization, a 90 degree polarization, a spiral polarization, a circular polarization, a vortex polarization, or an orbital angular momentum.

### Claim 8 (depends on 5)

The transceiver of claim 5, further comprising a polarization beam combiner (PBC) disposed between the first optical circulator and the first secondary laser.

### Claim 9 (depends on 8)

The transceiver of claim 8, further comprising a second secondary laser, wherein the first secondary laser is configured to modulate an x-component of the upstream modulated laser signal, and wherein the second secondary laser is configured to modulate a y-component of the upstream modulated laser signal.

### Claim 10 (depends on 9)

The transceiver of claim 9, wherein the laser injected modulator is configured to implement quadrature amplitude modulation.

### Claim 11 (depends on 10)

The transceiver of claim 10, further comprising:
a first optical splitter disposed between the PBC and the first secondary laser; and
a second optical splitter disposed between the PBC and the second secondary laser,
wherein the first secondary laser comprises a first sub-laser and a second sub-laser,
wherein the second secondary laser comprises a third sub-laser and a fourth sub-laser,
wherein the first sub-laser is configured to receive an I-signal of the x-component,
wherein the second sub-laser is configured to receive a Q-signal of the x-component,
wherein the third sub-laser is configured to receive an I-signal of the y-component,
wherein the fourth sub-laser is configured to receive a Q-signal of the y-component.

### Claim 12 (depends on 11)

The transceiver of claim 11, further comprising:
a first phase shift element disposed between the first optical splitter and the second sub-laser; and
a second phase shift element disposed between the second optical splitter and the fourth sub-laser.

### Claim 13 (depends on 5)

The transceiver of claim 5, further comprising:
a downstream receiver configured to process the downstream modulated signal on the first coherent tone; and
a second optical circulator in one-way communication with the first optical circulator and in two-way communication with the downstream receiver.

### Claim 14 (depends on 13)

The transceiver of claim 13, wherein the downstream receiver is a coherent receiver and is further configured to receive the downstream unmodulated signal on the second coherent tone as a local oscillator source.

### Claim 15 (depends on 13)

The transceiver of claim 13, wherein the downstream receiver is further configured to perform heterodyne detection.

### Claim 16 (depends on 13)

The transceiver of claim 13, wherein the downstream receiver comprises one or more of an integrated coherent receiver, an analog to digital converter, and a digital signal processor.

### Claim 17 (depends on 13)

The transceiver of claim 13, wherein the input laser signal further includes a plurality of downstream laser signals from the remote primary laser source, and wherein the downstream receiver is further configured to multiplex the plurality of downstream laser signals into a single received coherent signal.

### Claim 18 (depends on 1)

The transceiver of claim 1, comprising at least one of a termination unit, a customer device, a customer premises equipment, a modem, an optical network unit (ONU), a data center, and a virtualized cable modem termination system (vCMTS).

### Claim 19 (depends on 1)

The transceiver of claim 1, wherein the first and second coherent tones are a phase synchronized coherent tone pair, and wherein the first and second coherent tones are substantially confined to a narrow bandwidth of the single longitudinal mode of the remote primary laser source.

### Claim 20 (depends on 1)

The transceiver of claim 1, wherein the first secondary laser is configured to receive data from a first external data source to adhere into the output upstream modulated laser signal.