Summary of the technology
In a high bit rate optical transmission, the inclusion of a simple non-linear equalizer implementing the square-root mathematical function, just after the photo-detector and before the conventional electronic equalizer (FIR, MLSE, analog,..), linearizes the overall systems and highly improves the transmission performances.
It consists of obtaining a linear photo-receiver.
The intrinsic square-law non-linear function of the photodiode, relating the optical field amplitude and the generated current, can be partially compensated by means of the nonlinear electrical circuit performing a square-root function after the photodiode.
The results in long distance systems, with impairments like chromatic dispersion and ASE noise, have demonstrated a substantial performance enhancement, using FIR or MLSE equalizers in a digital IM-DD, and with Radio-over-Fiber systems.
The device has been implemented with fast shottky diodes in a simple structure, with a MMIC chip with technology GaAs 0.2 um, and with Digital Signal Processor, approximating the SQRT function with low error.
An extended version implements a modified function, that incorporates the optical noise model, and completely transforms it into Gaussian statistics at the photo-receiver output.
Current stage of development
Experimental prototype and validity tests passed.
Applications and Target Market
Optical transceiver manufacturers Broadband Telecom System Integrators Optical Communication networks: transport, metropolitan, access
Increased bandwidth x distance reach Simple and very low cost implementation, specially if integrated with TIA.
Increase of chromatic dispersion tolerance, by enhancement of conventional EDC capabilities (about +30%).
Linearization of the effect of other optical impairments, like reflections, optical noise, interferences, etc.
Eye diagram symmetry and transformation of ASE chi-square statistics into Gaussian.
Reduced number of required quantization levels for ADC.
Improved dynamic margin in FTTH PON burst-mode receivers.
Intellectual property status
Technology available for licensing, transfering and technical cooperation Patent Status Granted
Universitat Politècnica de Catalunya - UPC
Technology Transfer Office