Alcatel-Lucent Assigned Patent for Receiver Algorithms for Coherent Detection of Polarization-Multiplexed Optical Signals

The impact of Hurricane Sandy on the east coast of the United States proved to be no obstacle to the U.S. Patent and Trademark Office (USPTO), as it assigned an interesting patent to Alcatel-Lucent (News - Alert) for a “receiver algorithms for coherent detection of polarization-multiplexed optical signals.”

The abstract for the patent explains the essence of what this is:

A digital signal processor (DSP) operating within, for example, an optical receiver wherein the DSP processes complex sample streams derived from a modulated optical signal, the DSP configured to perform a method of acquiring an intermediate frequency (IF) signal from within the received optical signal, the method comprising: processing at least one block of complex sample stream symbols using a frequency locked loop (FLL) to achieve an initial constellation lock condition, the FLL having a nominal lock-in spectral region; if an initial constellation lock condition is not achieved within a predetermined amount of time, shifting the spectral region processed by the FLL to a spectral region proximate a current operating spectral region.

In layperson terms, this capability will allow for the more optimal management of optical signals than is currently available using existing solutions. Where this becomes most critical is in Polarization division multiplexed quadrature phase shift keying (PDM-QPSK). As the patent notes, this is considered an “attractive option for 100-Gb/s optically routed wavelength division multiplexed (WDM) transport systems.” 

In short, this is truly next-generation communications foundational art.

What is also important is the closing statement about product realization:

Although the DSP described herein is depicted as a general-purpose computer that is programmed to perform various control functions in accordance with the present embodiments, various embodiments may be implemented in hardware such as, for example, an application specific integrated circuit (ASIC) or a field-programmable gate array (FPGA)…Although various embodiments which incorporate the teachings of the present invention have been shown and described in detail herein, those skilled in the art can readily devise many other varied embodiments that still incorporate these teachings.

Again in non-engineering terms, the application of the intellectual property being assigned to Alcatel-Lucent is not only capable of being realized in product in a variety of ways and form factors, but is extensible for other potential uses in optical networking. 

Years ago, I was told that the one immutable trends of our time was that when it comes to networking, the need for speed will always be there and that those who at some point say we have too much capacity will always be wrong. In other words, confirmation of the line from the famous movie Field of Dreams about “if you build it they will come.” 

As we are seeing with all of the projections about the growth of data, filling up pipes with packets of bits and bytes is not going to be an issue. Making sure that all of that other IP (Internet Protocol) traffic is handled efficiently and effectively, however, will be a challenge, which is why the IP in this patent is likely to be important.