Pluggable optical transmitter module for network optical transport system with distortion control
View Patent ↗Linearized optical transmitter units are described for a hybrid optical fiber coaxial cable network. The linearized optical transmitter unit can comprise a directly-modulated or externally-modulated laser optically coupled to an optical conduit directed to an optical fiber communications link and electrically coupled to an electrical RF source line that provides an RF source to drive the laser or an external modulator for a light beam from the laser. A linearization information electrical component comprising memory and/or a processor, and a data output configured to transmit linearization enabling data for input into a direct digital synthesis engine that enables the direct digital synthesis engine to generate an RF signal wherein nonlinear responses of the transmitter and/or the optical fiber communications link are pre-compensated, in which the data is specific for the optical transmitter and/or the optical fiber communications link. An electronic communication channel can connected to the data output of the electrical component to communicate the linearization enabling data external to the linearized optical transmitter unit suitable for communication to the direct digital synthesis engine. The linearized optical transmitter can be assembled in a plug-in module. Corresponding HFC systems and methods are also described.
1. A pluggable optical transmitter module for providing an optical interface comprising:
a modulated laser optically coupled to an optical conduit directed to an optical fiber communications link and electrically coupled to an electrical RF source line that provides an RF source to drive the modulated laser;
an electrical storage/processing component comprising a digital processor, memory with stored predistortion parameters specific for the pluggable optical transmitter module and a data output configured to transmit pre-compensation data;
a communication channel connected to the data output of the electrical storage/processing component to carry the pre-compensation data specific for the pluggable optical transmitter module and/or the optical fiber communications link;
a housing containing the modulated laser and electrical storage/processing component;
an electrical plug connection providing an interface through the housing, the electrical plug connection comprising an RF signal input connection and a plurality of pin connectors wherein an RF signal input is in electrical connection with the directly-modulated laser or an external modulator for the externally-modulated laser through the electrical RF source line, and at least some of the pin connectors are in electrical connection with the communication channel wherein nonlinear responses of the pluggable optical transmitter module and/or the optical fiber communications link are communicated from the pluggable optical transmitter module such that they are available to pre-compensate the RF signal input based at least in part on predetermined pre-distortion parameters specific for the pluggable optical transmitter module and/or the optical fiber communications link based on the data transmitted over the communications channel; and
an optical connector providing an interface through the housing and designed for interfacing with an optical fiber or an optical fiber connector.
2. The pluggable optical transmitter module of claim 1 wherein the modulated laser comprises a directly-modulated distributed feedback laser.
3. The pluggable optical transmitter module of claim 1 wherein the modulated laser is an externally modulated laser that is modulated by a Mach-Zender modulator.
4. The pluggable optical transmitter module of claim 3 wherein the modulator is based on lithium niobate.
5. The pluggable optical transmitter module of claim 1 wherein the modulated laser is an externally modulated laser that is modulated by an electro-absorption modulator.
6. The pluggable optical transmitter module of claim 5 wherein the modulator is based on InP.
7. The pluggable optical transmitter module of claim 1 wherein the modulated laser is an externally-modulated laser, which is modulate by a modulator that is InP-based.
8. The pluggable optical transmitter module of claim 1 further comprising a temperature sensor wherein the temperature sensor provides temperature information to the digital processor.
9. The pluggable optical transmitter module of claim 1 further comprising a laser bias control operably connected to the digital processor wherein the laser bias control provides information on the laser bias voltage to the modulated laser.
10. The pluggable optical transmitter module of claim 1 further comprising an optical tap optically coupled to the optical conduit, an RF tap configured to receive RF signal from the electrical RF source line, and an optical receiver optically connected to the optical tap.
11. The pluggable optical transmitter module of claim 1 further comprising an RF amplifier.
12. The pluggable optical transmitter module of claim 1 wherein the predetermined predistortion parameters are transmitted in a format for reception by a direct digital synthesis engine.
13. The pluggable optical transmitter module of claim 1 further comprising a temperature controller.
14. The pluggable optical transmitter module of claim 1 further comprising a voltage bias controller electrically connected to the modulated laser and to the digital processor for adjustment of the predistortion parameters.
15. The pluggable optical transmitter module of claim 1 further comprising a transformer connecting the RF input and the modulated laser to provide improved impedance matching of an optical laser modulator.
16. The pluggable optical transmitter module of claim 1 further comprising an RF attenuator receiving RF signal from the corresponding connector pin.
17. The pluggable optical transmitter module of claim 1 further comprising an RF tap, RF signal detector configured to direct a portion of the RF signal to the digital processor.
18. The pluggable optical transmitter module of claim 1 further comprising a light tap and a receiver, wherein the light tap is configured to direct a portion of laser output to a receiver and the receiver is configured to direct a corresponding signal to the digital processor.
19. The pluggable optical transmitter module of claim 1 having a length from about 50 mm to about 150 mm, a width from about 10 mm to about 25 mm and a height from about 5 mm to about 12 mm.