Distributed travelling-wave mach-zehnder modulator driver

Abstract

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.