Abstract: An optical system and method for seeding an optical transmitter includes a first optical transmitter comprising a first reflective optical amplifier and a second optical transmitter comprising a second reflective optical amplifier. The second optical transmitter is optically coupled to the first optical transmitter. The optical system also includes an optical cavity for seeding the first reflective optical amplifier with a first optical seed signal. The optical cavity is formed between the first reflective optical amplifier of the first optical transmitter and the second reflective optical amplifier of the second optical transmitter. The first reflective optical amplifier is configured to transmit a first optical signal to the second reflective optical amplifier and the second reflective optical amplifier is configured to provide the first optical seed signal by reflecting a portion of the first optical signal back to the first reflective optical amplifier.

Abstract: An optical system and method for seeding an optical transmitter includes a first optical transmitter comprising a first reflective optical amplifier and a second optical transmitter comprising a second reflective optical amplifier. The second optical transmitter is optically coupled to the first optical transmitter. The optical system also includes an optical cavity for seeding the first reflective optical amplifier with a first optical seed signal. The optical cavity is formed between the first reflective optical amplifier of the first optical transmitter and the second reflective optical amplifier of the second optical transmitter. The first reflective optical amplifier is configured to transmit a first optical signal to the second reflective optical amplifier and the second reflective optical amplifier is configured to provide the first optical seed signal by reflecting a portion of the first optical signal back to the first reflective optical amplifier.

Abstract: An optical source comprises a first laser arranged to generate a first optical signal having a first state of polarization (SOP) and a first optical frequency; a second laser arranged to generate a second optical signal having a second SOP, substantially orthogonal to the first SOP, and having a second optical frequency, different from the first optical frequency by a preselected frequency difference; a polarisation beam coupler arranged to combine the first optical signal and the second optical signal into a composite optical signal comprising both the first optical signal and the second optical signal having said substantially orthogonal SOPs; and an output arranged to output the composite optical signal.

Abstract: An optical source comprises a first laser arranged to generate a first optical signal having a first state of polarization (SOP) and a first optical frequency; a second laser arranged to generate a second optical signal having a second SOP, substantially orthogonal to the first SOP, and having a second optical frequency, different from the first optical frequency by a preselected frequency difference; a polarisation beam coupler arranged to combine the first optical signal and the second optical signal into a composite optical signal comprising both the first optical signal and the second optical signal having said substantially orthogonal SOPs; and an output arranged to output the composite optical signal.

Abstract: An optical source (10) comprising: a first laser (12) arranged to generate a first optical signal (14) having a first state of polarization and a first optical frequency; a second laser (16) arranged to generate a second optical signal (18, 48, 78) having a second state of polarization, substantially orthogonal to the first state of polarization, and having a second optical frequency, different to the first optical frequency by a preselected frequency difference, ??; a polarization beam coupler (20) arranged to combine the first optical signal and the second optical signal into a composite optical signal comprising both the first optical signal and the second optical signal having said substantially orthogonal states of polarization; and an output (22) arranged to output the composite optical signal (24).

Abstract: An optical source (10) comprising: a first laser (12) arranged to generate a first optical signal (14) having a first state of polarization and a first optical frequency; a second laser (16) arranged to generate a second optical signal (18, 48, 78) having a second state of polarization, substantially orthogonal to the first state of polarization, and having a second optical frequency, different to the first optical frequency by a preselected frequency difference, ??; a polarization beam coupler (20) arranged to combine the first optical signal and the second optical signal into a composite optical signal comprising both the first optical signal and the second optical signal having said substantially orthogonal states of polarization; and an output (22) arranged to output the composite optical signal (24).

Abstract: An optical access network comprises an optical network unit having a first port for connecting to a first optical link, a second port for connecting to a second optical link and an optical source. The optical source is arranged to generate a first optical signal, to transmit the first optical signal via the first port, to receive an optical seed signal via the first port and to amplify the optical seed signal. The optical seed signal has a narrower bandwidth compared to the first optical signal. A modulator is arranged to modulate the amplified optical seed signal with upstream data to form an upstream optical signal and to transmit the upstream optical signal via the second port. A polarisation modifier can modify polarisation of the first optical signal.

Abstract: In a coherent optical receiver, a received signal and an oscillator-generated signal, having frequency difference such that the receiver operates under intradyne conditions, are made to beat in a 3×3 optical coupler. A polarizing beam-splitter splits one of the signals into components with orthogonal polarization which are applied to inputs of the coupler, which receives the other of the received or oscillator-generated signal. After photoelectric conversion, the signals are fed to analog processing devices generating an electrical signal representing the received signal that is fed to a low pass filter before being demodulated. The frequency difference between the signals and the passband of the filter are such that a component of the electrical signal, oscillating at a frequency depending on the frequency difference and having amplitude and phase depending on the instant state of polarization of the received signal, is suppressed. A method is also provided.

Abstract: An optical source (10) comprising: a first laser (12) arranged to generate a first optical signal (14) having a first state of polarisation and a first optical frequency; a second laser (16) arranged to generate a second optical signal (18, 48, 78) having a second state of polarisation, substantially orthogonal to the first state of polarisation, and having a second optical frequency, different to the first optical frequency by a preselected frequency difference, Av; a polarisation beam coupler (20) arranged to combine the first optical signal and the second optical signal into a composite optical signal comprising both the first optical signal and the second optical signal having said substantially orthogonal states of polarisation; and an output (22) arranged to output the composite optical signal (24).

Abstract: An optical access network comprises an optical network unit having a first port for connecting to a first optical link, a second port for connecting to a second optical link and an optical source. The optical source is arranged to generate a first optical signal, to transmit the first optical signal via the first port, to receive an optical seed signal via the first port and to amplify the optical seed signal. The optical seed signal has a narrower bandwidth compared to the first optical signal. A modulator is arranged to modulate the amplified optical seed signal with upstream data to form an upstream optical signal and to transmit the upstream optical signal via the second port. A polarisation modifier can modify polarisation of the first optical signal.

Abstract: In a coherent optical receiver, a received signal and an oscillator-generated signal, having frequency difference such that the receiver operates under intradyne conditions, are made to beat in a 3×3 optical coupler. A polarising beam-splitter splits one of the signals into components with orthogonal polarisation which are applied to inputs of the coupler, which receives the other of the received or oscillator-generated signal. After photoelectric conversion, the signals are fed to analogue processing devices generating an electrical signal representing the received signal that is fed to a low pass filter before being demodulated. The frequency difference between the signals and the passband of the filter are such that a component of the electrical signal, oscillating at a frequency depending on the frequency difference and having amplitude and phase depending on the instant state of polarisation of the received signal, is suppressed. A method is also provided.

Abstract: An optical access network comprises an optical network unit having a first port for connecting to a first optical link, a second port for connecting to a second optical link and an optical source. The optical source is arranged to generate a first optical signal, to transmit the first optical signal via the first port, to receive an optical seed signal via the first port and to amplify the optical seed signal. The optical seed signal has a narrower bandwidth compared to the first optical signal. A modulator is arranged to modulate the amplified optical seed signal with upstream data to form an upstream optical signal and to transmit the upstream optical signal via the second port. A polarization modifier can modify polarization of the first optical signal.

Abstract: Optical transmitter apparatus 10 comprising a reflective optical amplifier 12, a driver 14, an optical splitter 16, polarisation compensation apparatus 18 and an optical router 20. The reflective optical amplifier is arranged to receive an optical seed signal. The driver is arranged to generate a drive signal arranged to cause the reflective optical amplifier to amplify the optical seed signal to form an optical signal. The optical splitter is arranged to receive the optical signal and to split off a part of the optical signal to form a further optical signal. The polarisation compensation apparatus is arranged to receive the further optical signal and to rotate a polarisation of the further optical signal by a pre-determined amount, to form a further optical seed signal. The optical router is arranged to receive the further optical seed signal and to direct the further optical seed signal to the reflective optical amplifier for amplification thereby.

Abstract: An optical access network comprises an optical network unit having a first port for connecting to a first optical link, a second port for connecting to a second optical link and an optical source. The optical source is arranged to generate a first optical signal, to transmit the first optical signal via the first port, to receive an optical seed signal via the first port and to amplify the optical seed signal. The optical seed signal has a narrower bandwidth compared to the first optical signal. A modulator is arranged to modulate the amplified optical seed signal with upstream data to form an upstream optical signal and to transmit the upstream optical signal via the second port. A polarisation modifier can modify polarisation of the first optical signal.

Abstract: An optical access network comprises an optical line terminal and an optical network unit having a transmitter. An optical path connects an output of the transmitter of the optical network unit to the optical line terminal. The transmitter of the optical network unit is arranged to transmit an upstream signal with an amplitude modulation format having at least one level transition per data bit period for at least one of the logical bits and a frequency modulation occurring with the level transition. An optical filter is positioned in the optical path. A central wavelength of a response of the optical filter has an offset with respect to a wavelength of the upstream signal. The wavelength of the upstream signal is located on a slope of the response of the optical filter.

Abstract: An optical network unit (10) comprising a reflective semi-conductor optical amplifier (R-SOA) 12 and a driver 14. The R-SOA has a large optical confinement factor and is arranged to receive a portion of a downstream optical signal having a signal wavelength and a signal power. The driver is arranged to generate a drive signal 16 to drive the R-SOA. The drive signal is arranged to cause the R-SOA to operate in saturation at the signal power. The drive signal is further arranged to cause the R-SOA to apply a return-to-zero line code to said portion of the downstream optical signal to form an upstream optical signal at the signal wavelength. The drive signal is further arranged to cause the R-SOA to apply a phase modulation to the upstream optical signal.

Abstract: A reflective optical network (10) comprises an optical network unit (14) and an optical receiver (22). The optical network unit (14) comprises a reflective optical modulator (16) arranged to receive a seed optical signal, and a transmitter controller (18) arranged to receive a data signal (20) and to control the modulator (16) to apply the data signal (20) to the seed optical signal, to form an optical data signal. The transmitter controller (18) is arranged to process the data signal (20) to substantially prevent the optical data signal comprising spectral components at frequencies lower than a cut-off frequency, being the frequency at which a power spectral density of said optical data signal is lower than a peak power spectral density of said optical signal by a cut-off power value. The optical receiver (22) comprises an electrical domain high pass filter (26) having a cut-off frequency higher than a linewidth of the seed optical signal.

Abstract: Optical transmitter apparatus 10 comprising a reflective optical amplifier 12, a driver 14, an optical splitter 16, polarisation compensation apparatus 18 and an optical router 20. The reflective optical amplifier is arranged to receive an optical seed signal. The driver is arranged to generate a drive signal arranged to cause the reflective optical amplifier to amplify the optical seed signal to form an optical signal. The optical splitter is arranged to receive the optical signal and to split off a part of the optical signal to form a further optical signal. The polarisation compensation apparatus is arranged to receive the further optical signal and to rotate a polarisation of the further optical signal by a pre-determined amount, to form a further optical seed signal. The optical router is arranged to receive the further optical seed signal and to direct the further optical seed signal to the reflective optical amplifier for amplification thereby.

Abstract: A distribution node of a passive optical network (PON) comprises a first port for receiving a first optical continuous envelope modulated downstream data signal at a first wavelength (?C) from a first optical line termination unit (OLT1) and a second port for receiving a second optical continuous envelope modulated downstream data signal at a second wavelength (?L) from a second optical line termination unit (OLT2). A first converter (FBG-1) performs continuous envelope modulation-to-intensity modulation conversion of the first optical downstream data signal and forwards the converted first optical downstream data signal (?C) to the first group of optical network units (ONU1 . . . N). A second converter (FBG-2) performs continuous envelope modulation-to-intensity modulation conversion of the second optical downstream data signal and forwards the converted second optical downstream data signal (?L) to the second group of optical network units (ONUN+1 . . . 2N).

Abstract: The invention relates to improvements in or relating to modulation in an Optical Network, and to an apparatus, a method and a communications network for modulation in an Optical Network. An apparatus is arranged to receive a modulated optical signal comprising a carrier wavelength and first data. The apparatus is arranged to substantially erase the first data from the optical signal by performing an inversion operation on the modulated optical signal. The apparatus is arranged to receive second data and to modulate the carrier wavelength with the second data for onward transmission of the second data. The inversion operation comprises applying a signal comprising an inverse of the first data to at least a portion of the modulated optical signal. The signal may further comprise the second data such that the modulation of the carrier wavelength and erasure of the first data is performed in a single operation.