Optical communication with predistortion to compensate for odd order distortion in modulation and travel

A signal predistorting circuit for laser communications through an optical fiber, comprising;

• signal input means for providing an electronic signal for information communications;
• in-line signal predistorting means to electronically predistort the electronic signal prior to using the electronic signal to modulate a laser beam to convett the electronic signal to an optical signal, for compensating for odd order distortion of the optical signal due to the optical signal traveling through optical fiber;
• means for dynamically adjusting the predistortion to compensate for changes in the length of the optical fiber to reduce the distortion of the optical signal at a receiver at a distal end of the fiber from the laser when the length of the optical fiber is changed;
• signal output means for providing the predistorted electronic signal to a laser for producing the laser beam.

A laser transmitter comprising:

• signal input means for providing an electronic signal;
• a laser for producing a laser beam with a predetermined wavelength of light;
• in-line signal predistorting means to electronically predistort the electronic signal prior to using the electronic signal to modulate the laser beam to convert the electronic signal into an optical signal, for compensating for odd order distortion due to the optical signal traveling through zero dispersion fiber;
• means for modulating the laser beam;
• an optics system for directing the modulated laser beam into the optical fiber.

An information communication system, comprising

• a network of optical fibers;
• a first node and second local node communicating through an optical fiber network, each comprising:
• means for providing an output electronic information signal;
• in-line signal predistorting circuit means to electronically predistort the output electronic signal to produce a predistorted electronic signal, for compensating for odd order distortion due to the optical output signal traveling from the first node to the second node through the optical fiber network;
• a laser for producing the output laser beam with a predetermined wavelength of light;
• means to modulate the output laser beam with the predistorted electronic signal;
• an optics system for directing the modulated output laser beam into a first one of the optical fibers as an output fiber to transmit the optical output signal;
• an optical detector for converting an optical input signal into an input electronic signal;
• and
• additional compensation means for electronically compensating for even order distortions due to using The electronic signal to modulate the laser beam, and for compensating for even order distortions due to the optical signal traveling through the optical fiber from the first node to the second local node;
• and whereby optical signals are communicated bidirectionally between the first node and the second node and the optical information signal has higher distortion at the means to modulate than at the optical detector.

A cable television network, comprising:

• a network of optical fibers;
• and
• a head-end including:
• program means for receiving a multitude of television programs;
• gateway means for data communications with other types of networks including a telephone network for receiving and transmitting telephone communications and computer networks for transmitting and receiving computer information;
• modulator means for modulating the television programs and the data communications received from the gateway means with multiple carriers each television program having a carrier at a different respective frequency and the data communications using multiple carriers with different respective frequencies;
• combiner means for combining multiple carriers into one or more electronic forward signals;
• a respective laser for each forward signal, for producing a respective forward laser beam with a predetermined wavelength of light;
• respective means for modulating each laser beam with the electronic forward signal to convert the electronic forward signal to a respective optical forward signal;
• respective in-line signal predistorting means for each electronic forward signal, including an electronic circuit to predistort the electronic forward signal prior to using the electronic signal to modulate the forward laser beam, for compensating for odd order distortion due to the optical forward signal traveling through optical fiber;
• a respective optics system for each laser, for directing the modulated forward laser beam into respective ones of the optical fibers for each laser beam;
• respective detector means for converting one or more optical return signals from respective ones of the optical fibers, into electronic return signals;
• means for providing the electronic return signals as data communications to the gateway means for transmitting the return signals as telephone communications and computer information;
• and
• the network further comprising:
• a multitude of separate coaxial cable network trees;
• a plurality of local nodes, each connected to one or more optical fibers and one or more coaxial cable networks, each local node including:
• respective means for converting one or more optical forward signals from respective ones of the optical fibers, into respective electronic forward signals in one or more coaxial cable networks;
• return signal separation means including a respective diplex filter for each coaxial cable network, for separating return data signals from the electronic forward signals in the respective coaxial cable network;
• a return laser for each electronic return signal, for producing a respective return laser beam with a predetermined wavelength of light;
• return signal predistorting means for each electronic return signal, including an electronic circuit to predistort the electronic return signal prior to using the electronic signal to modulate the return laser beam to convert the electronic return signal into an optical return signal, for compensating for odd order distortion due to modulating the return laser beam and for compensating for odd order distortion due to the optical return signal traveling through optical fiber;
• a multitude of customer interface units connected to the coaxial cable network trees for receiving the forward information signals and for transmitting return data signals, including;
• means for connecting a television display to the coaxial cable network tree for displaying the television programs;
• means for connecting telephone equipment to the coaxial cable network for receiving and transmitting telephone communications and for connecting computer equipment to the coaxial cable network for transmitting and receiving computer information.

A method for optical communication comprising:

• receiving an electronic information signal;
• adjusting a signal predistorting circuit for the length of an optical fiber through which the information signal will be transmitted;
• in-line predistorting the electronic information signal using an in-line circuit to compensate for odd order distortion of the optical signal due to the optical signal traveling through optical fiber, so that the odd order distortion at a receiver at a distal end of the optical fiber from the laser is reduced;
• producing a laser beam using a laser;
• modulating the laser beam using the electronic information signal to produce an optical information signal;
• transmitting the optical information signal to travel through the optical fiber to an optical receiver;
• whereby the optical information signal in the optical fiber has lower odd order distortion at the optical receiver than at the laser.