Digital-to-analog converter and generation of high-bandwidth analog signals

An apparatus to create a high-bandwidth analog signal, the apparatus comprising:

• a controlled switch having N inputs and a single output, where N is an integer greater than or equal to two, the controlled switch being switchable between N different states, where in each state a respective one of the N inputs is connected to the single output;
• and
• N sources of sub-streams of analog samples, each sub-stream composed of pairs of adjacent analog samples, each one of the N sources coupled to a respective one of the N inputs;
• where, in operation, the controlled switch is controlled by a control signal to switch between the N different states so that while the controlled switch is in any one of the N different states, a data transition occurs between two adjacent analog samples in the sub-stream whose source is coupled to the input that is connected to the single output,
• wherein the single output yields the high-bandwidth analog signal, and any pair of adjacent analog samples in any one of the N sub-streams substantially determines a corresponding pair of adjacent analog samples in the high-bandwidth analog signal.

A transmitter comprising:

• a symbol source operative to generate a stream of symbols representing data to be transmitted in an optical signal;
• a digital signal processor (DSP) operative to process the symbols output from the symbol source and to generate first digital drive signals and second digital drive signals;
• a first digital-to-analog converter (DAC) operative to convert the first digital drive signals to first analog drive signals;
• a second DAC operative to convert the second digital drive signals to second analog drive signals;
• a laser operative to generate an optical carrier;
• a polarizing beam splitter operative to split the optical carrier into orthogonally-polarized components;
• a first electrical-to-optical modulator operative to modulate one of the orthogonally-polarized components according to the first analog drive signals to produce a first modulated polarized optical signal;
• a second electrical-to-optical modulator operative to modulate another of the orthogonally-polarized components according to the second analog drive signals to produce a second modulated polarized optical signal;
• and
• a beam combiner operative to combine the first modulated polarized optical signal and the second polarized optical signal into the optical signal,
• wherein the first DAC comprises:
• a controlled switch having N inputs and a single output, where N is an integer greater than or equal to two, the controlled switch being switchable between N different states, where in each state a respective one of the N inputs is connected to the single output;
• a partitioning module operative to partition the first digital drive signals into N sub-streams of digital samples, each sub-stream of digital samples composed of pairs of adjacent digital samples;
• and
• N sub-DACs, each one of the N sub-DACs operative to convert a sub-stream of digital samples into a respective one of N sub-streams of analog samples, each sub-stream of analog samples composed of pairs of adjacent analog samples, each one of the N sub-DACs coupled to a respective one of the N inputs;
• where, in operation, the controlled switch is controlled by a control signal to switch between the N different states so that while the controlled switch is in any one of the N different states, a data transition occurs between two adjacent analog samples in the sub-stream whose source is coupled to the input that is connected to the single output, and
• wherein the single output yields the first analog drive signals, and any pair of adjacent analog samples in any one of the N sub-streams substantially determines a corresponding pair of adjacent analog samples in the first analog drive signals.