DISTRIBUTED TRAVELLING-WAVE MACH-ZEHNDER MODULATOR DRIVER
A distributed traveling-wave Mach-Zehnder modulator driver having a plurality of modulation stages that operate cooperatively (in-phase) to provide a signal suitable for use in a 100 Gb/s optical fiber transmitter at power levels that are compatible with conventional semiconductor devices and conventional semiconductor processing is described.
1 - 19 . (canceled)
20 . A modulator, comprising:
an optical input waveguide for receiving an input optical signal and splitting the input optical signal into a first portion and a second portion;
a plurality of sequential modulators connected to the optical input waveguide for receiving the first portion and the second portion;
an optical output port for recombining the first portion and the second portion into a modulated output optical signal;
a differential electrical data input connected to a data source;
a plurality of driver-amplifier stages, each including a respective differential driver amplifier input, a respective differential driver amplifier output, and a respective differential signal output connected to a respective one of the sequential modulators, the respective differential driver amplifier input of a first of the plurality of driver-amplifier stages connected to the differential electrical data input; and
a plurality of delay/relay stages, each including a respective differential delay/relay input connected to the respective differential driver amplifier output of a previous one of the plurality of driver-amplifier stages, and a differential delay/relay output connected to the respective differential driver amplifier input of a following one of the plurality of driver-amplifier stages;
wherein an optical delay of each of the plurality of sequential modulators plus optical waveguide wiring matches a delay between the driver-amplifier stages so that modulations constructively add.
21 . The modulator according to claim 20 , wherein each respective differential signal output is configured to comprise an open-collector driver for driving sequential modulators with different impedances.
22 . The modulator according to claim 20 , wherein each respective differential signal output is configured to comprise an open-collector cascode driver for driving the sequential modulators with different impedances.
23 . The modulator according to claim 22 , wherein each respective differential signal output is configured to comprise an open-collector driver for driving the sequential modulators with both 25Ω and 50Ω impedances.
24 . The modulator according to claim 20 , further comprising:
a plurality of DC bias structures, each DC bias structure configured to individually control one of said plurality of delay/relay stages;
wherein each DC bias structures is configured to control an on state and an off state of a respective delay/relay stage for shutting down individual delay/relay stages.
25 . The modulator according to claim 24 , wherein the DC bias structures are also configured to control on and off states of a respective on of the plurality of driver-amplifier stages for shutting down individual driver amplifier stages.
26 . The modulator according to claim 24 , wherein each DC bias structures is also configured to control variation in biasing voltages of a respective one of the driver-amplifier stages.
27 . The modulator according to claim 20 , further comprising:
a plurality of DC bias structures, each DC bias structure configured to individually control one of the plurality of driver amplifier stages;
wherein each DC bias structures is configured to control an on state and an off state of a respective one of the driver-amplifier stages for shutting down individual driver amplifier stages.
28 . The modulator according to claim 27 , further comprising:
wherein each DC bias structures is also configured to control variation in biasing voltages of a respective one of the driver-amplifier stages.
29 . The modulator according to claim 20 , further comprising:
a plurality of DC bias structures, each DC bias structure configured to individually control one of the plurality of driver amplifier stages;
wherein each DC bias structures is configured to control variation in biasing voltages of a respective one of the driver-amplifier stages.
30 . The modulator according to claim 20 , wherein each one of the driver-amplifier stages includes only a single type of transistor to enable high-speed operation.
31 . The modulator according to claim 20 , wherein each one of the plurality of driver amplifier stages includes a pre-amplifier stage.
32 . The modulator according to claim 20 , wherein the plurality of sequential modulators comprise a plurality of optical phase-shifter pairs connected in series.
33 . The modulator according to claim 32 , wherein each one of the plurality of phase-shifter pairs comprises a fixed optical length.
34 . The modulator according to claim 32 , wherein each one of the plurality of optical phase shifter pairs comprises a Mach-Zehnder interferometer modulator.
35 . The modulator according to claim 20 , wherein each of the first portion and the second portion comprise equal intensities.
36 . The modulator according to claim 20 , wherein the plurality of driver amplifier stages comprises four, and the plurality of delay/relay stages comprises three.
37 . The modulator according to claim 20 , wherein each one of the plurality of driver amplifier stages includes:
a first pair of emitter followers including termination resistors connected to the respective differential driver amplifier input;
a pre-amplifier comprising a differential pair;
a buffer comprising a second pair of emitter followers; and
means for splitting a differential input signal into first and second differential output signals for output the respective differential driver amplifier output, and the respective differential signal output, respectively.
38 . The modulator according to claim 20 , wherein the plurality of sequential modulators, the optical input waveguide, and the optical output port are integrated on a semiconductor chip; and wherein the differential electrical data input, the plurality of driver amplifier stages, and the plurality of delay/relay stages comprise drive circuitry attached to the semiconductor chip.
39 . The modulator according to claim 38 , further comprising flip-chip bump bonding for attaching the drive circuitry to the semiconductor chip.