Abstract:
A method for optical layer traffic grooming includes receiving at least two optical input signals into respective optical receivers, each optical receiver having a photodetector for converting the respective optical input signal into a respective electrical signal; a grooming processor responsive to the electrical signals, the grooming processor being a radio frequency RF processor for processing the electrical signals at a subcarrier level to produce an RF orthogonal frequency division multiplexing signal OFDM signal; and modulating the groomed RF OFDM signal at a transmitter for conversion of the groomed RF OFDM into an optical signal.
Abstract:
The present invention employs a look up table based implementation for the metric computations which eliminate redundancy and substantially reduce the number of multiplications. Moreover, inventive method exploits the fact that the un-normalized constellation symbols are complex integers so that the product of a real-number and an un-normalized constellation symbol can be implemented by only additions. The inventive method also enables a greater efficiency for whitening colored noise prior to demodulation, one of which involves no square-root operation. The invention results in less complexity, faster operation, lower power consumption, without sacrificing performance.
Abstract:
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.
Abstract:
Methods and systems for secure communication include assigning data streams to respective orthogonal sub-carriers according to random number information at a transmitter. The data streams are modulated onto the respective orthogonal sub-carriers before the orthogonal sub-carriers are transmitted. The random number information is transmitted on a second medium, separate from the transmission medium. The orthogonal sub-carriers are received from the transmission medium at a receiver, while the random number information is received from the second medium at the receiver. The orthogonal sub-carriers are associated with data streams using the random number information and demodulated to produce data for the associated data stream.
Abstract:
Methods and devices for compensating for chromatic dispersion are shown that include receiving an input data signal, applying a filter to the data signal, and outputting a CD compensated signal. Applying the filter includes convolving known filter coefficients with a plurality of delayed versions of the data signal using addition and at least one inverse sign operation or using lookup tables and combining outputs to produce a CD compensated signal.
Abstract:
Systems and methods are disclosed for providing media access control (MAC) in an optical network by providing a separate control channel and data channel; dedicating each optical network unit (ONU) with one control channel, wherein the control message is transmitted at any time without constraints; sending a grant message to an ONU just before an allocated time is about to start; and sending data traffic from the ONU immediately after receiving the grant message without synchronizing with an optical line terminal (OLT) clock.
Abstract:
A pneumatic ratchet wrench is connected with an air supply device and contains: a housing, a ratchet head unit, an impact clutch unit, and a driving unit. The housing extending along a first axis line and includes an opening defined on a front end thereof and an intake formed on a distal end thereof so as to couple with an air supply device. The ratchet head unit is received in the housing and includes a drive square extending along a second axis line and extending out of the opening The impact clutch unit is received in the housing and is coupled with the ratchet head unit. The driving unit is disposed in the housing and includes a multi-chamber cylinder, a rotor member inserted into the multi-chamber cylinder and connecting with the impact clutch unit. The multi-chamber cylinder has a body, a first chamber, and a second chamber communicating with the first chamber.
Abstract:
A method by an optical OFDM receiver includes converting a received optical signal to an electrical signal, deriving a digital signal from the electrical signal, and emulating, with an iterative OFDM demodulator responsive to the digital signal, a transmitter effect in the received signal of lower peak clipping and top peak distortion and applying the transmitter effect to the received signal and a decision-made signal for estimating an error function to be applied to a demodulation of the received optical signal.
Abstract:
A coded multidimensional modulation system called generalized OFDM (GOFDM) uses orthogonal subcarriers as bases functions, and the signal constellation points of corresponding multidimensional constellation diagram are obtained as N-dimensional Cartesian product of one-dimensional PAM/two-dimensional QAM. In GOFDM, the N-dimensional/2N-dimensional signal constellation point is transmitted over all N subcarriers/2N-subcarriers, which serve as individual bases functions. Even if some of the subcarriers are severely affected by channel distortion, the overall signal constellation point will face only small distortion, when strong channel capacity achieving channel codes are used. In addition, because the channel capacity is a linear function of number of dimensions, the spectral efficiency of optical transmission systems is significantly improved. Finally, since Euclidean distance of multidimensional signal constellation is much larger that that of two-dimensional signal constellations, OSNR sensitivity is dramatically improved.
Abstract:
Systems and methods for generating an image are provided. These systems and methods include generating multiple light beams from a light source by controlling at least one parameter of the light source to be different among each of the multiple light beams. The systems and methods further include forming multiple light patterns of circuit structures that are separated in frequency by directing each of the light beams at a mask of circuit features. The systems and methods, when used in lithography for example, further include directing each of the light patterns toward a silicon substrate. The silicon substrate includes a silicon wafer having a surface at least partially covered with at least one of a photoresist material and a reversible contrast enhancement material (R-CEM).