Google Inc.

Xiangjun Zhao

Cedric Fung Lam

Changhong Joy Jiang

Liang Du

Tao Zhang

Shuang Yin

Daoyi Wang

Adam Edwin Taylor Barratt

Muthu Nagarajan

Claudio Desanti

Yut Loy Chan

Steven Fong

Chiachi Wang

Ke Dong

Hong Liu

Ryohei Urata

Ben Warren Segura

Pedram Zare Dashti

Satrukaan Sivagnanasuntharam

Adam Edwin Taylor Ward Barratt

A method () for tuning a tunable laser () includes delivering a bias current (I) to an anode of a distributed Bragg reflector (DBR) section diode (D) disposed on a shared substrate of the tunable laser and receiving a burst mode signal () indicative of a burst-on state or a burst-off state. When the burst mode signal is indicative of the burst-off state, the method includes offsetting the bias current at the anode of the DBR section diode by one of sourcing a push current with the bias current to the anode of the DBR section diode or sinking a pull current away from the bias current at the anode of the DBR section diode. When the burst mode signal is indicative of the burst-on state, the method also includes ceasing any offsetting of the bias current at the anode of the DBR section diode.

Switching circuit for burst-mode tunable laser

A method () of biasing a tunable laser () during burst-on and burst-off states includes receiving a burst mode signal () indicative of the burst-on state or the burst-off state and when the burst mode signal is indicative of the burst-on state: delivering a first bias current (I) to an anode of a gain-section diode () disposed on a shared substrate of the tunable laser; and delivering a second bias current (I) to an anode of phase-section diode () disposed on the shared substrate. The second bias current is less than the first bias current. When the burst mode signal transitions to be indicative of the burst-off state, the method also includes delivering the first bias current to the anode of the gain-section diode; and delivering the second bias current to the anode of the phase-section diode wherein the first bias current is less than the second bias current.

Wavelength drift suppression for burst-mode tunable EML laser

A method () includes a gain current (I) to an anode of a gain-section diode (D) disposed on a shared substrate of a tunable laser (), delivering a modulation signal to an anode of an Electro-absorption section diode (D) disposed on the shared substrate of the tunable laser, and receiving a burst mode signal () indicative of a burst-on state or a burst-off state. When the burst mode signal is indicative of the burst-off state, the method includes sinking a sink current (I) away from the gain current at the anode of the gain-section diode. When the burst mode signal transitions to be indicative of the burst-on state from the burst-off state, the method includes ceasing the sinking of the sink current away from the gain current and delivering an overshoot current (I) to the anode of the gain-section diode.

Burst mode laser driving circuit

A method () includes delivering a first bias current (I) to an anode of gain-section diode () and delivering a second bias current (I) to an anode of a phase-section diode (). The method also includes receiving a burst mode signal () indicative of a burst-on state or a burst-on state, and sinking a first sink current (I) away from the first bias current when the burst mode signal is indicative of the burst-off state. When the burst mode signal transitions to be indicative of the burst-on state from the burst-off state, the method also includes sinking a second sink current away from the second bias current at the anode of the phase-section diode and ceasing the sinking of the first sink current away from the first bias current at the anode of the gain section diode.

Wavelength drift suppression for burst-mode tunable EML transmitter

A method of combining optical signals from a plurality of optical fibers into a single optical signal includes receiving, at corresponding optical-signal receivers optically coupled to corresponding trunk fibers, respective optical signals. The method further includes determining, by the corresponding optical-signal receivers, when each respective optical signal is received. When the respective optical signal is received, the method includes performing the following steps: converting, by the corresponding optical-signal receiver, the respective optical signal to a corresponding electrical signal; transmitting, by the corresponding optical-signal receiver, the corresponding electrical signal to a corresponding input channel of an electrical-multiplexing device; and configuring the electrical-multiplexing device to select the corresponding input channel. Configuring the electrical-multiplexing device to select the corresponding input channel causes the electrical-multiplexing device to transmit the corresponding electrical signal to an electro-optical converter configured to convert the corresponding electrical signal back to the respective optical signal.

Port replicator

A method of establishing communication between an optical line terminal and an optical network unit within an optical access network includes receiving a signal indication from an optical transceiver of an optical line terminal. The signal indication includes: (i) a loss-of-signal indication indicating non-receipt of an upstream optical signal from the optical network unit; or (ii) a signal-received indication indicating receipt of the upstream optical signal from the optical network unit. The method includes determining whether the signal indication includes the loss-of-signal indication. When the signal indication includes the loss-of-signal indication, the method includes instructing the optical transceiver to cease signal transmission from the optical transceiver to the optical network unit. Moreover, when the signal indication includes the signal-received indication, the method includes instructing the optical transceiver to transmit a downstream optical signal from the optical transceiver to the optical network unit.

Optical network unit wavelength tuning

A method for in-field calibration of a laser transmitter includes receiving, at an optical network unit (ONU), a downstream connection from an optical line terminal (OLT) where the ONU includes a Distributed Bragg Reflector (DBR) laser. The method further includes attempting to establish an upstream connection between the ONU and the OLT. When the ONU establishes the upstream connection to the OLT, the method also includes receiving, at the ONU, a message to initiate calibration of the ONU where the message is generated to indicate that the DBR laser is operating outside an operational state. The method further includes tuning, by the ONU, the DBR laser to the operational state by adjusting an injection current for the DBR laser.

In-field calibration of laser transmitter

A remote node includes a first node input, a second node input, and an optical switch. The optical switch includes a first switch input optically coupled to the first node input, a second switch input optically coupled to the second node input, a first switch output switchably coupled to the first switch input or the second switch input, and a second switch output switchably coupled to the first switch input or the second switch input. The remote node includes a photodiode optically coupled to the second switch output, and a capacitor electrically coupled to the photodiode and the optical switch. When the first switch input is switchably coupled to the first switch output, the second switch input is switchably coupled to the second switch output. Light received by the second switch input passes out the second switch output to the photodiode. The photodiode charges the capacitor to a threshold charge.

Feeder fiber and central office redundancy

A method for biasing a tunable laser during burst-on and burst-off states through a common-cathode laser driving circuit includes delivering a bias current to an anode of a gain-section diode having a shared substrate with the laser, and receiving a burst mode signal indicative of a burst-on state or a burst-off state. When the burst mode signal is indicative of the burst-off state, the method includes sinking a sink current away from the anode of the gain-section diode. The sink current is less than the bias current delivered to the anode of the gain-section diode. When the burst mode signal transitions to be indicative of the burst-on state from the burst-off state, the method includes ceasing the sinking of the sink current away from the anode of the gain-section diode, and delivering an overshoot current to the anode of the gain-section diode to accelerate heating of the gain-section diode.

Common cathode laser driving circuit

A carrier office includes an optical line terminal, a first transmit-erbium-doped fiber amplifier (EDFA), and a second transmit-EDFA. The OLT is configured to transmit first and second optical signals. The first transmit-EDFA is optically coupled to the OLT and a first feeder fiber, and the first feeder fiber is optically coupled to a first remote node (RN). The first transmit-EDFA is operable between a respective enabled state and a respective disabled state. The second transmit-EDFA is optically coupled to the OLT and a second feeder fiber, and the second feeder fiber is optically coupled to a second RN. The second transmit-EDFA is operable between a respective enabled state and a respective disabled state.

A system includes a multiplexer having a pass-band and an optical network unit (ONU) optically coupled to the multiplexer. The ONU includes a tunable laser configured to continuously transmit an optical signal to the multiplexer in a burst-on state and a burst-off state. While in the burst-on state, the ONU is configured to tune the tunable laser to transmit the optical signal at a transmit wavelength within the wavelength pass-band of the multiplexer. The multiplexer configured to allow passage therethrough of the optical signal at the transmit wavelength. While in the burst-off state, the ONU is configured to tune the tunable laser to transmit the optical signal at a non-transmit wavelength outside of the wavelength pass-band of the multiplexer. The multiplexer configured to block passage therethrough of the optical signal at the non-transmit wavelength.

Tunable laser in an optical access network

The communication system has first and second optical systems and an optical feed fiber in communication with the first optical system and arranged to convey a feeder optical signal to the second optical system. The first optical system includes a multiplexer configured to multiplex/demultiplex between a first optical line terminal signal, a second optical line terminal signal, and the feeder optical signal. The feeder optical signal includes the first optical line terminal signal and the second optical line terminal signal. The first optical line terminal signal includes a first upstream free spectral range and a first downstream free spectral range. The second optical line terminal signal includes a second upstream free spectral range and a second downstream free spectral range. The second optical system is in communication with the optical feed fiber and is configured to multiplex and demultiplex between the feeder optical signal and optical network unit signals.

Upgrading PON systems using a multi-cycle field AWG

A method includes receiving a mode control signal indicative of a current-mode or a voltage-mode. When the mode control signal is indicative of the voltage-mode, the method includes connecting a voltage-mode bias sub-circuit to an anode of a reflector-section diode and applying an adjustable bias voltage to bias a diode voltage at the anode of the reflector-section diode. The reflector-section diode is disposed on a shared substrate of a tunable laser. When the mode control signal is indicative of the current-mode, the method includes connecting a current-mode bias sub-circuit to the anode of the reflector-section diode and delivering an adjustable bias current to the anode of the reflector-section diode.

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Fremont, CA, United States of America

Xiangjun Zhao