This disclosure relates generally to the field of telecommunications and in particular to methods and apparatus' for dynamic intra-channel receiving of optical telecommunication signals.
Optical superchannel is an emerging technology that supports optical transport data rates in excess of 100-Gb/s by combining multiple optical subcarriers to create a composite optical signal exhibiting a desired capacity. Advantageously, optical superchannel technology may allow network operators to realize improved spectral efficiency, greater node-switching flexibility, and lower costs.
An advance in the art is made according to an aspect of the present disclosure directed to methods and apparatus for receiving optical superchannels. In sharp contrast to the prior art which employ a number of large bandwidth front-end coherent receivers that each receive neighboring optical subcarriers of an optical superchannel, the methods and apparatus of the present disclosure receive multiple, non-neighboring optical subcarriers of an optical superchannel at a single optical receiver at the same time. Such methods according to the present disclosure we call dynamic intra-channel receiving.
Advantageously, while optical superchannel methods and apparatus according to the present disclosure may only require a single optical receiver to receive non-neighboring optical subcarriers, prior art methods and apparatus require multiple receivers to receive such non-neighboring subcarriers comprising a received superchannel.
In an exemplary embodiment, multiple local oscillators are provided to a single coherent receiver front-end such that different optical sub-carriers that are spaced apart in frequency are down-converted to a baseband in a single operation. Through the effect of optical signal/local oscillator arrangement by filtering and laser tuning, our method and apparatus advantageously minimize any cross talk from non-dropped channels.
A more complete understanding of the present disclosure may be realized by reference to the accompanying drawings in which:
The following merely illustrates the principles of the disclosure. It will thus be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the disclosure and are included within its spirit and scope.
Furthermore, all examples and conditional language recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the disclosure and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions.
Moreover, all statements herein reciting principles, aspects, and embodiments of the disclosure, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently-known equivalents as well as equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure.
Thus, for example, it will be appreciated by those skilled in the art that the diagrams herein represent conceptual views of illustrative structures embodying the principles of the invention.
In addition, it will be appreciated by those skilled in art that any flow charts, flow diagrams, state transition diagrams, pseudocode, and the like represent various processes which may be substantially represented in computer readable medium and so executed by a computer or processor, whether or not such computer or processor is explicitly shown.
In the claims hereof any element expressed as a means for performing a specified function is intended to encompass any way of performing that function including, for example, a) a combination of circuit elements which performs that function or b) software in any form, including, therefore, firmware, microcode or the like, combined with appropriate circuitry for executing that software to perform the function.
The invention as defined by such claims resides in the fact that the functionalities provided by the various recited means are combined and brought together in the manner which the claims call for. Applicant thus regards any means which can provide those functionalities as equivalent as those shown herein. Finally, and unless otherwise explicitly specified herein, the drawings are not drawn to scale.
Thus, for example, it will be appreciated by those skilled in the art that the diagrams herein represent conceptual views of illustrative structures embodying the principles of the disclosure.
By way of some additional background, it is initially noted that prior art designs of superchannel systems employ multiple receivers since the optical signal bandwidth of the superchannel is too wide for a single optical receiver. Typically each receiver of these prior art superchannel systems receive a single optical sub-carrier—or multiple sub-carriers if the multiple sub-carriers are adjacent to one another in frequency. Of course, such systems require that the multiple sub-carriers so received “fit” into the receiver bandwidth.
As may be readily appreciated by those skilled in the art, these prior art approaches to superchannel systems present particular problems for network switching nodes since it is not always the case that neighboring subcarriers are dropped at a particular receiving node. Consequently, if desired drop subcarriers are not immediate neighbors to one another in frequency—such prior art superchannel systems are unable to receive the subcarriers simultaneously thereby requiring dedicated, multiple receivers.
Advantageously, superchannel systems according to the present disclosure permit non-neighboring sub-carriers to be received simultaneously by a single receiver—which we have previously noted that we call dynamic intra-channel receiving.
Turning now to
As shown further in
As will now be apparent to those skilled in the art and with reference to
Accordingly, the superchannel signal is first optically, selectively filtered such that the two subchannels (#2 and #9) are applied to a signal port of the single coherent receiver which has applied to its local oscillator port (LO port) two local oscillator signals, namely LO 1 and LO2. Additionally, the applied LO signals (LO 1 and LO 2) are not centered at the subcarrier frequencies. Instead, the frequencies of the applied LO signals are offset such that down-converted subcarriers do not overlap and therefore create interference in baseband. As an illustrative example—and as depicted in
Turning now to
As depicted in
As depicted, the symmetric optical interleaver has a single input to which is applied the superchannel signal and two outputs which are further connected to two inputs of a wavelength selective switch. The two outputs of the interleaver contain the “odd” and “even” groups of the superchannel which are applied to a respective input of the wavelengfth selective switch (WSS).
The WSS, upon receiving the odd and even groups of the superchannel signal output by the symmetric interleaver will pick or otherwise separate out the two subcarriers needed for receiving. These two subcarriers are then applied to a single coherent receiver which includes two local oscillators (LO 1, LO 2) applied as described previously. Advantageously, a sharp filtering edge of the optical interleaver insures that interference from immediate neighboring subcarriers—in this instance subcarrier #1 and subcarrier #10—is reduced or minimized. As before, the LO frequency(ies) are not coincident with the centers of the subcarrier frequencies rather they are offset. More particularly, and as depicted in
Notably, and with reference now to
As depicted in this example, the superchannel signal is applied to an input of a symmetric interleaver the output of which is directed to the inputs of a wavelength selective switch. The wavelength selective switch selects the three subcarriers to be dropped and applies those signals to a single coherent receiver having a single input and three distinct local oscillators namely, LO 1, LO 2, and LO 3.
As depicted in this example shown in
While this disclosure has been shown and described using particular examples, those skilled in the art will readily appreciate that the disclosure contemplates application beyond the illustrative examples shown. Accordingly, the disclosure should be viewed as limited only by the scope of the claims that follow.
This application claims the benefit of United States Provisional Patent Application Ser. No. 61/489,509 filed May 24, 2011 which is incorporated by reference as if set forth at length herein.
Number | Date | Country | |
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61489509 | May 2011 | US |