Method, apparatus and system for high-speed transmission on fiber optic channel
View Patent ↗Multi-carrier modulation fiber optic systems constructed using a series of electrical carriers, modulating the data on the electrical carriers and combining the carriers to form a wideband signal. The wideband signal can then be intensity modulated on a laser and coupled to a fiber optic channel. A receiver may then receive the laser signal from the fiber optic channel and convert it into an electrical signal. Multi-carrier modulation may be applied to existing fiber channels, which may be of lower quality. Existing fiber channels may have characteristics which prevent or restrict the transmission of data using intensity modulation at certain frequencies. An adaptive multi-carrier modulation transmitter may characterize an existing fiber optic channel and ascertain the overall characteristics of the channel. The transmitter and receiver can then be configured to use various bandwidths and various modulations in order to match the transfer characteristic of the fiber channel. A series of adaptive multi-carrier modulation transmitters and receivers can be integrated on a single integrated circuit. If multiple adaptive receivers and transmitters are integrated on a single integrated circuit, they may be used to upgrade existing networks by adding different wavelength lasers for the transmission of data in order to achieve any capacity desired. Each receiver and transmitter may characterize the fiber for its particular wavelength laser and may configure the modulation and bandpass to the fiber's characteristics.
1. An apparatus for receiving data from a channel, the apparatus comprising:
a mixer operable to accept a wideband signal and mix it with a mixer frequency;
a low-pass filter operable to filter the output of the mixer;
a programmable demodulator operable to accept the output of the filter, demodulate said filter output, and provide soft decisions as an output, the programmable demodulator comprising a control input that controls the type of demodulation applied to the signal accepted from the low-pass filter; and
a trellis decoder operable to accept soft decisions from the demodulator, perform a trellis decoding of the soft decisions, and provide hard decisions.
2. The apparatus as in claim 1 , wherein the mixer frequency is a programmable frequency.
3. The apparatus as in claim 1 , wherein the output of the mixer has an in-phase component and a quadrature-phase component.
4. The apparatus as in claim 1 , wherein the trellis decoder is operable to reduce inter-symbol interference.
5. The apparatus as in claim 1 , wherein the trellis decoder is operable to reduce attenuation and phase distortion introduced by the channel.
6. The apparatus as in claim 1 , wherein the type of demodulation is based on the encoding applied in each symbol, and wherein an increase in the number of bits in a symbol decreases symbol error rate.