摘要:
A high-speed optical transmitter comprises multiple digital lanes that are provided to a bank of digital-to-analog converters. The analog signals are then used to Phase Shift Keyed (PSK) modulation using a Chirp Managed Laser (CML)-based transmitter, and potentially using dual polarization. A corresponding optical receiver receives the sequence of optical signals at a demodulator. For each polarization, the demodulator includes a corresponding demodulation channel that is configured to demodulate that polarization component of the optical signal into one or more signal components. Each of these signal components is converted into a corresponding digital signal using a corresponding analog-to-digital converter. In the case of higher-order PSK modulation (e.g., 8PSK or higher), for each polarization, the analog converter has a lower sampling rate than for QPSK modulation.
摘要:
An wave division multiplexed (WDM) optical transmitter is disclosed including a directly modulated laser array and a planar lightwave chip (PLC) having a plurality of OSRs that receive outputs of the laser array and increase the extinction ratio of the received light. An optical multiplexer receives the outputs of the OSRs and couples them to a single output port. The multiplexer has transmission peaks through its ports each having a 0.5 dB bandwidth including the frequency of a laser in the array. The optical multiplexer may be embodied as cascaded Mach-Zehnder interferometers or ring resonators.
摘要:
This invention provides a flat dispersion frequency discriminator (FDFD) capable of having a substantially flat dispersion with either a positive or negative dispersion along the spectrum region of the discriminator. This way, a FDFD may not cause substantial distortion of the intensity patter of its output to minimize the occurrence distortion due to overshooting or undershooting of the intensity pattern depending on the relative spectral alignment of the laser output relative to the filter transmission.
摘要:
A fiber optic communication system comprising: an optical signal source adapted to receive a binary base signal having a bit period T, and generate a first signal, wherein the first signal is frequency modulated; and an optical spectrum reshaper (OSR) adapted to reshape the first signal into a second signal, wherein the second signal is amplitude modulated and frequency modulated; characterized in that: the frequency excursion of the first signal is adjusted such that the frequency excursion is substantially equal to the ratio of the bit period of the digital base signal to total dispersion of the transmission fiber, whereby to increase the tolerance of the second signal to dispersion in a transmission fiber.
摘要:
Optical signal produced by a semiconductor electroabsorption modulator is passed through an optical discriminator to increase the optical and electrical modulation response of the device and decrease the output chirp for distortionless transmission through dispersive optical fiber.
摘要:
A DBR laser, such as a semiconductor DBR laser is disclosed having improved frequency modulation performance. The laser includes a split gain electrode and a tuning electrode. A modulating current encoding a data signal is injected into a first section of the gain electrode whereas a substantially DC bias voltage is imposed on a second section of the gain electrode positioned between the first gain electrode and the tuning electrode. The first and second gain electrodes are electrically isolated from each other and the tuning electrode by a large isolation resistance. In some embodiments, the isolation resistance is generated by forming the electrodes on a P+ layer and removing portions of the P+ layer between adjacent electrodes. Capacitors may couple to one or both of the second gain electrode and the tuning electrode.
摘要:
Apparatus and methods for driving a transmitter to generate DNPSK signals is disclosed including generating N data streams comprising data symbols and for each of a plurality of sets of N simultaneous data symbols of the N data streams, imposing signals are on L of a plurality of signal lines, with the value of L corresponding to values of the N simultaneous data symbols. Signals on the plurality of signal lines are ANDed with a clock signal synchronized with the N data streams to produce RZ signals. The RZ signals are summed and the summed signal is input to a laser that produces an output having frequency modulation corresponding to the magnitude of the summed signal. The output of the laser is passed through an optical discriminator.
摘要:
The optical signal produced by a modulated semiconductor laser is passed through a fiber grating optical discriminator to increase the modulation response of the device and decrease the output chirp for transmission through optical fiber. In one embodiment, a simple pulse source comprises a directly modulated single mode semiconductor laser and a fiber Bragg grating filter. A single-mode semiconductor laser, such as, a distributed feed-back laser is driven by the addition of a DC bias current and a sinusoidal current at the desired bit rate. The output of the laser is passed through a low pass or high pass fiber Bragg grating filter with a sharp edge to produce nearly transform limited pulses. Stabilization of a laser apparatus is included.
摘要:
An apparatus and method for measuring the spectral dependence of the Raman gain coefficient in optical fibers is presented. This approach measures the power level of Raman scattering in both a walk-off limited region and a physical fiber length limited region and, from these measurements, extracts the spectral dependence of the Raman gain coefficient. Access to these two regions is accomplished through control of the excitation pulse temporal width and relies on fiber dispersion to separate the excitation light from the Raman scattered light for short pulse widths. This approach measures the spectral dependence of the Raman gain without the necessity of absolute power measurement of the Raman scattered light, the need for a reference standard, or the need of a frequency tunable secondary optical source.
摘要:
An wave division multiplexed (WDM) optical transmitter is disclosed including a directly modulated laser array and a planar lightwave chip (PLC) having a plurality of OSRs that receive outputs of the laser array and increase the extinction ratio of the received light. An optical multiplexer receives the outputs of the OSRs and couples them to a single output port. The multiplexer has transmission peaks through its ports each having a 0.5 dB bandwidth including the frequency of a laser in the array. The optical multiplexer may be embodied as cascaded Mach-Zehnder interferometers or ring resonators.