摘要:
An optical transmitter includes a dividing optical coupler, a first optical modulator driven by an I component of a first signal and a I component of a second signal for modulating a lightwave, a DC bias of the first optical, a second optical modulator driven by a Q component of the first signal and a Q component of the second signal for modulating a lightwave, a DC bias of the second optical modulator, a phase shifter, and a combining optical coupler for combining the modulated lightwave from the first optical coupler and the phase shifted Q components of the first and second signals for generating a quadrature amplitude modulated signal.
摘要:
A method and system for generating multi-subcarriers is disclosed. Re-circulating frequency shifters—based on the frequency shifting in two cascading phase modulators—are used to generate 112 subcarriers with stable architecture since there is no direct current bias in phase modulators.
摘要:
Methods and systems for receiving an optical signal using cascaded frequency offset estimation. Coherently detecting an optical signal includes compensating for a coarse laser frequency offset between a transmitting laser and a local oscillator laser by determining a maximum phase error (MPE) in the optical signal, compensating for a residual laser frequency offset between the transmitting laser and the local oscillator laser, and decoding data stored in the optical signal.
摘要:
An optical apparatus includes a quadrature phase shift keying modulator for generating a non-return-to-zero quadrature phase shift keyed NRZ-QPSK signal from a received lightwave, the modulator being driven by a radio frequency RF signal, an intensity modulator for carving the NRZ-QPSK signal to return-to-zero RZ pulses with a different duty cycle than that of the NRZ-QPSK, the intensity modulator being driven by a radio frequency RF clock signal to change the NRZ-QPSK to an RZ-QPSK signal, and an optical filter with a narrow band for filtering the signal from the intensity modulator to increase optical power that is useable by an optical digital coherent detection system.
摘要:
A system and method to adjust the symbol constellation used to de-map a signal in an optical coherent communications system. A feedback de-mapper adjustment module is configured to compare average Error Vector Magnitude and Bit Error Ratio to a pre-defined table to determine when a constellation de-mapper mismatch occurs. The feedback de-mapper adjustment module then rotates the de-mapper constellation in order to compensate for phase drift.
摘要:
A passive optical network (PON) device, system and method include an optical line terminal (OLT) receiver configured to receive multiple signals at different wavelengths simultaneously and enable multiple transmitters to operate at the same time during one upstream time slot. The optical line terminal employs Orthogonal Frequency Division Multiple Access (OFDMA) to transparently support a plurality of applications and enable dynamic bandwidth allocation among these applications where the bandwidth is allocated in two dimensional frequency and time space.
摘要:
An optical system and method includes a source-free optical network unit coupled to an optical fiber for receiving an original carrier signal with downstream data over the optical fiber. The optical network unit includes a modulator configured to remodulate the original carrier signal with upstream data to produce an upstream data signal for transmission back down the optical fiber in a direction opposite to a direction in which that original carrier signal was received.
摘要:
A method for generating a 400 Gb/s single channel optical signal from multiple modulated subchannels includes carving respective modulated subchannels into return-to-zero RZ modulated subchannels having non-overlapping peaks with intensity modulators having a duty cycle less than 50%, and combining the subchannels into a single channel signal aggregating the bit rate of each of the subchannels. The subchannels are combined with a flat top optical component for increased subsequent receiver sensitivity.
摘要:
A time to digital converter (TDC) is able to be utilized for measuring a time interval between two signals with a very fine time resolution, which is defined as the difference in propagation delay per stage between two rings or chains of delay stages. The Vernier ring TDC, Vernier TDC with comparator matrix or Vernier ring TDCs with comparator matrix comprise two rings or chains of delay stages with slightly different propagation delays per stage and a plurality of comparators for comparing two signals propagation along two rings or chains and determining when the lag signal passes the lead signal. The lead and lag signal are initiated by two events and are each fed into a separate one the first stages of one of the specified rings or chains. The comparators are able to be organized in a comparator matrix in order to occupy less space and permit reuse. As a result, the input time interval (the time between the two initiating events) is able to be measured through the product of the time resolution and the number of stages through which the two signals propagated.
摘要:
An optical system for providing all-optical up-conversion of a baseband signal including an all-optical up-converter responsive to baseband signals to provide corresponding dual sideband signals about a suppressed optical carrier, said dual sideband signals each having the same polarization direction, being phase locked, having the same optical power and having a fixed frequency spacing; and an optical filter for filtering the carrier signals and providing wavelength division multiplexed signals without optical carriers. In a preferred embodiment, the all-optical up-converter includes an intensity modulator for generating two pump lightwaves that are carrier suppressed in response to the intensity modulator receiving a laser light source and being driven by an RF signal, wherein the intensity modulator is DC biased at a null point, an optical combiner for combining the baseband signal and the two pump lightwaves, a nonlinear medium for four wave mixing the baseband signal and two pump lightwaves to generate the baseband signal and corresponding dual sideband signals, and an optical interleaver for removing the baseband signal and two pump lightwaves to provide said sideband signals about the suppressed optical carrier.