A first signal is generated from an input signal by a first delay (70), and by low pass filtering (74). A second signal is generated from the input signal and from a second, longer delayed (72), version of the input signal, such that in response to a pulse on the input signal, the second signal has a sequence of two pulses, coinciding respectively with leading and trailing edges of a corresponding pulse on the first signal. If the signals are electrical, they can drive I and Q inputs of an IQ modulator (84, 86). If generated optically, they can be combined directly to produce the encoded optical output signal. By using such delays and filtering to produce these signals, a CAPS-3 encoded optical signal can be simulated, to obtain its chromatic dispersion tolerance advantages with less complex hardware and less power consumption.

An optical wireless transmission device according to an embodiment of the present invention comprises: a modulation unit for receiving input of a first input signal and outputting a first output signal; and a light source control unit for controlling a first light source in accordance with the first output signal. The first output signal repeats 0 and 1 in a first phase during clock time if a binary value of the first input signal is 0, and repeats 0 and 1 in a phase opposite from the first phase during the clock time if a binary value of the first input signal is 1.

A first signal is generated from an input signal by a first delay (70), and by low pass filtering (74). A second signal is generated from the input signal and from a second, longer delayed (72), version of the input signal, such that in response to a pulse on the input signal, the second signal has a sequence of two pulses, coinciding respectively with leading and trailing edges of a corresponding pulse on the first signal. If the signals are electrical, they can drive I and Q inputs of an IQ modulator (84, 86). If generated optically, they can be combined directly to produce the encoded optical output signal. By using such delays and filtering to produce these signals, a CAPS-3 encoded optical signal can be simulated, to obtain its chromatic dispersion tolerance advantages with less complex hardware C and less power consumption.

A receiver circuit is disclosed and is configured to receive an optical signal. The receiver circuit includes a receiving circuit configured to receive the optical signal and convert the optical signal from a duobinary signal format into a binary signal based on a plurality of decision thresholds. The receiver circuit also includes a clock data recovery circuit configured to sample the binary signal per data period at a first time instant based on a predetermined clock data recovery technique, and sample the binary signal per data period at a second time instant offset from the first instant, as well as determine an intermediate sample based on an offset for decoding a transmitted bit sequence according to soft information based on the samples.

The method of transmitting data includes encoding, at an optical line terminal, data to be transmitted over a plurality of wavelength channels; providing the encoded data to corresponding lasers as modulation inputs, to enable the lasers to generate optical signals representing the data; multiplexing the optical signals; and equalizing the multiplexed optical signals for transmission via an optical transmission link. The method of receiving data includes de-multiplexing, at an optical network unit, optical signals received from an optical transmission link; selecting, from the de-multiplexed optical signals, an optical signal corresponding to a particular wavelength channel; converting the selected optical signal into electric signals; and decoding the electric signal to determine the data.

A PON having an OLT configured to send downlink transmissions to ONUs using amplitude modulation and two symbol rates. An example ONU includes a clock-recovery circuit capable of continuous clock extraction from the received variable-rate modulated optical signal. The continuous clock extraction can be achieved, e.g., by (i) configuring the photodetector to convert the higher-rate portions of the received optical signal into transformed electrical waveforms while converting the lower-rate portions thereof into similar electrical waveforms and (ii) configuring the clock-recovery circuit to phase-align the clock signal with signal transitions in the resulting sequence of transformed and similar electrical waveforms. An ONU configured to operate in this manner can advantageously stay locked to the received data signal during transmissions at both symbol rates, without the need to reacquire the clock signal at each rate change and/or at the beginning of each packet intended for the host ONU.

Disclosed are a data transmission device for modulating the amplitude of a PAM-4 signal using a toggle serializer and a method of operating the same. In accordance with an embodiment of the present disclosure, the data transmission device includes a toggle serializer configured to generate at least one toggle signal by detecting logic level change of first and second signals from a Pulse Amplitude Modulation (PAM) signal including the first and second signals; and a driver configured to modulate an amplitude of the PAM signal by combining the first signal, the second signal, and the at least one toggle signal.

A receiver circuit is disclosed and is configured to receive an optical signal. The receiver circuit includes a receiving circuit configured to receive the optical signal and convert the optical signal from a duobinary signal format into a binary signal based on a plurality of decision thresholds. The receiver circuit also includes a clock data recovery circuit configured to sample the binary signal per data period at a first time instant based on a predetermined clock data recovery technique, and sample the binary signal per data period at a second time instant offset from the first instant, as well as determine an intermediate sample based on an offset for decoding a transmitted bit sequence according to soft information based on the samples.

The invention discloses an optical transmission device based on direct-sequence-spread-spectrum time-division-multiple-access, which includes a signal transmitting module and a signal receiving module. The transmitting module is connected with the receiving module by optical fibers. The transmitting module is used for receiving an external data sequence signal, encoding the external data sequence signal into a direct-sequence-spread-spectrum time-division-multiple-access electric signal and modulating the resulting electric signal into corresponding spread-spectrum optical signal for transmission by optical fibre. The receiving module is used for receiving the direct-sequence-spread-spectrum time-division-multiple-access optical signal, and sequentially performing photoelectric conversion, analog despreading, analog-digital conversion and clock recovery to obtain the external data sequence signal. The invention realizes direct-sequence-spread-spectrum modulation supporting direct detection; at a receiving end, the despreading in analog domain removes impairments and improves sensitivity. The interleaved configuration of the up-link and down-link chip sequences and dynamic ranging through the time-division-multiple-access protocol realize the interleaved transmission of bytes.

A reflective modulator which comprises a coupler, two diodes and two DC block units. The coupler has an input end used to output an output signal, an output end used to output an output signal, a first load end connected to one of the diodes and a second load end connected to another one of the diodes. The DC block units connect between the diodes and the coupler for DC blocking. A message signal is selectively inputted to both of the two DC block units for operating the state of the two diodes. The two diodes turn on when the message signal is large enough. The two diodes turn off when the message signal is not large enough. The two diodes are implemented by PIN diodes. A BPSK modulator using the reflective modulator and a quadrature modulator using the BPSK modulator is also introduced.