Abstract: Various embodiments relate to bi-directional optical communication. An optical system may include a first transceiver module including at least one transmitter and at least one receiver, wherein each transmitter of the at least one transmitter is configured to transmit a first signal via an optical fiber and at a wavelength. The optical system may further include a second transceiver module configured to communicate with the first transceiver module via the optical fiber and including at least one transmitter and at least one receiver, wherein each transmitter of the at least one transmitter of the second transceiver module is configured to transmit a second signal via the optical fiber and at another, different wavelength.

Abstract: A method of transmitting data may include receiving feedback information that includes effective channel bandwidths, signal-to-noise ratios (SNRs) associated with multiple optical channels on an optical link, and individual SNRs associated with subcarriers on each optical channel. The method may include determining multiple subcarrier power allocation schemes based on the feedback information. Each subcarrier power allocation scheme may be associated with a corresponding optical channel from the multiple optical channels and may be configured to allocate a signal power among subcarriers configured to transmit on the corresponding optical channel. The method may include determining, based on the feedback information, an optical power allocation scheme configured to allocate an optical power among the multiple optical channels. The method may include transmitting data on the multiple optical channels based on the multiple subcarrier power allocation schemes and the optical power allocation scheme.

Abstract: A method of blind tap coefficient adaptation includes receiving a digital data signal including random digital data, equalizing a first portion of the digital data signal using a first set of predetermined tap coefficients and a second portion of the digital data signal using a second set of predetermined tap coefficients. The method includes generating a first eye diagram and a second eye diagram from a first portion and a second portion of an equalized signal, respectively. The first eye diagram is compared with the second eye diagram to determine which of the sets of predetermined tap coefficients results in a data signal having a higher signal quality. The method includes inputting to an equalizer as an initial set of tap coefficients the first set of predetermined tap coefficients or the second set of predetermined tap coefficients according to the determination.

Abstract: A method of blind tap coefficient adaptation includes receiving a digital data signal including random digital data, equalizing a first portion of the digital data signal using a first set of predetermined tap coefficients and a second portion of the digital data signal using a second set of predetermined tap coefficients. The method includes generating a first eye diagram and a second eye diagram from a first portion and a second portion of an equalized signal, respectively. The first eye diagram is compared with the second eye diagram to determine which of the sets of predetermined tap coefficients results in a data signal having a higher signal quality. The method includes inputting to an equalizer as an initial set of tap coefficients the first set of predetermined tap coefficients or the second set of predetermined tap coefficients according to the determination.

Abstract: A method of transmitting data may include receiving feedback information that includes effective channel bandwidths, signal-to-noise ratios (SNRs) associated with multiple optical channels on an optical link, and individual SNRs associated with subcarriers on each optical channel. The method may include determining multiple subcarrier power allocation schemes based on the feedback information. Each subcarrier power allocation scheme may be associated with a corresponding optical channel from the multiple optical channels and may be configured to allocate a signal power among subcarriers configured to transmit on the corresponding optical channel. The method may include determining, based on the feedback information, an optical power allocation scheme configured to allocate an optical power among the multiple optical channels. The method may include transmitting data on the multiple optical channels based on the multiple subcarrier power allocation schemes and the optical power allocation scheme.

Abstract: A method of blind tap coefficient adaptation includes receiving a digital data signal including random digital data, equalizing a first portion of the digital data signal using a first set of predetermined tap coefficients and a second portion of the digital data signal using a second set of predetermined tap coefficients. The method includes generating a first eye diagram and a second eye diagram from a first portion and a second portion of an equalized signal, respectively. The first eye diagram is compared with the second eye diagram to determine which of the sets of predetermined tap coefficients results in a data signal having a higher signal quality. The method includes inputting to an equalizer as an initial set of tap coefficients the first set of predetermined tap coefficients or the second set of predetermined tap coefficients according to the determination.

Abstract: A method of blind tap coefficient adaptation includes receiving a digital data signal including random digital data, equalizing a first portion of the digital data signal using a first set of predetermined tap coefficients and a second portion of the digital data signal using a second set of predetermined tap coefficients. The method includes generating a first eye diagram and a second eye diagram from a first portion and a second portion of an equalized signal, respectively. The first eye diagram is compared with the second eye diagram to determine which of the sets of predetermined tap coefficients results in a data signal having a higher signal quality. The method includes inputting to an equalizer as an initial set of tap coefficients the first set of predetermined tap coefficients or the second set of predetermined tap coefficients according to the determination.

Abstract: A test has been developed that is known as the transmitter waveform dispersion penalty (TWDP) test. The TWDP test has been used to test and certify various optical data transmission devices. Similar tests are being developed to test optical receivers such as a difference waveform distortion penalty (dWDP). A test pattern used to generate the transmitted sequence by the device under test is a PRBS9. The PRBS9 test pattern begins with a run of nine ones and has a length of 511 bits. According to the teachings herein, a test pattern of less than 511 bits is generated to perform the TWDP and dWDP tests. The test pattern may include a sequence of bits specifically designed to provide reliable test penalty calculation without the costly and time consuming aspects of the conventional TWDP and dWDP tests using the PRBS9 pattern.

Abstract: A mode-mixer is used to introduce mode-mixing to an input in an optical coupler. As a result, modal noise effects are minimized in an output of the optical coupler. An example of a mode-mixer implemented includes a step index optical fiber which may or may not be coupled to a graded index optical fiber via a splice within an optical coupler. The splice may be a mechanical splice using connectors or a fused splice in some embodiments. The optical coupler may be included in a system for monitoring and/or analyzing a network.

Abstract: An optical equaliser, for use in an optical communications system, comprises a plurality of concatenated, fixed modulation depth, periodic filters. Each of the filters may be individually dynamically wavelength tuned in order to optimise optical equalisation of an optical signal transmitted by an optical element in the optical communications system.

Abstract: An optical data transmission system using a Mach Zehnder (M-Z) modulator asymmetrically modulates the optical carrier to generate control information to optimize the transmitted optical signal.

Abstract: A method of tagging individual wavelength division multiplexed channels within a plurality of said channels. The method comprises the step of creating a tagging tone in the form of an analogue spectral line tone, by providing a series of regularly spaced time slots substantially throughout each of said tagged channels for receipt of binary tagging pulses. The binary tagging pulses in each tagged channel are arranged in a different manner to provide a characteristic tag for each tagged channel.

Abstract: An optical equalizer comprises a plurality of serially concatenated filter elements the phase and modulation depth of which can be individually tuned. The filter elements are tuneable in order to generate a desired optical equalization function. Each of the filter elements is a three arm interferometer and each is fabricated utilizing integrated waveguide technology.

Abstract: A multi-mode pump laser having an output, and an optical fiber coupler. The optical fiber coupler has a first section and a second section. The first section of the optical fiber coupler comprises a multi-mode fiber which is optically coupled to the pump laser output. The second section of the fiber coupler comprises a plurality of single mode optical fibers each of which has an input which is optically coupled to the multi-mode fiber. The source further comprises a pump drive which is controllable to dither the optical center frequency of the light produced by the pump laser, so as to scramble modal power distribution at the inputs of the single mode optical fibers.

Abstract: At a receiver a 20 Gbit/s soliton bit stream is demultiplexed into two 10 Gbit/s bit streams using a 2-way splitter, a clock extraction circuit, and a pair of polarization insensitive amplitude modulators exhibiting positive chirp. The outputs of the modulators are fed to detectors via lengths of optical fiber exhibiting normal dispersion thereby producing bit streams with increased mark/space ratio and reduced timing jitter.

Abstract: One facet of each of a set of N semiconductor laser chips is provided with an antireflection coating through which the chip emission is coupled, via a wavelength multiplexer, with a partially reflecting Bragg reflector providing an N-way wavelength multiplexed laser output for pumping an optical amplifier. The wavelength multiplexer may be constituted by a cascade arrangement of Mach-Zehnders.

Abstract: In an optical TDM transmission system in which a set of N tributary channels at one bit rate are multiplexed on to a single multiplexed channel at N times the bit rate of the tributary channels, an amplitude modulation with a fundamental frequency matched to a subharmonic of the tributary bit rate is impressed on the multiplexed signal. At the demultiplexer this modulation is detected to provide a clock for separating the tributary channels in a manner which directs specific tributary channels to specific outputs without having to have recourse to reading any of the transmitted data itself.

Abstract: An interferometric optical multiplexer 10 for use in optical communication systems and especially for use in optical communication systems employing fibre optical amplifiers is disclosed. The interferometric optical multiplexer has two input ports 12, 14, an output port 16 and an output monitoring port 18. The interaction of the input signals is monitored by a photodetector situated in the monitoring part 18. In conjunction with a feedback circuit 24 wavelength separation of signals input at pods 12, 14 is ensured.