Abstract: An optical time-domain reflectometer, OTDR, apparatus is configured to measure a backscattered trace of a fiber link under test (FLUT). The OTDR apparatus includes at least one photo diode adapted to detect an optical signal reflected from points along the fiber link under test in response to an optical test signal generated by a laser of the OTDR apparatus and supplied to the fiber link under test. The reflected optical test signal is attenuated or amplified automatically such that the power of the optical signal received by the photodiode is limited to a predetermined power range.

Abstract: A method for generating a tone signal (TS) having a tone frequency, f, wherein the method comprises the following steps: supplying (S1) a binary bit stream (BBS) having a mark pattern with a supply bit rate, BR, to a signal filter unit; and filtering (S2) the supplied binary bit stream (BBS) by said signal filter unit to generate the tone signal (TS), wherein the mark pattern of the binary bit stream (BBS) supplied to said signal filter unit is adapted to minimize a ratio of the supply bit rate, BR, to the tone frequency, f, of the generated tone signal (TS).

Abstract: A method for creating an optical binary digital transmit signal to be supplied to an optical transmission link including: operating an optical transmitter in such a state that mode hopping occurs between a predefined first and a predefined second optical mode of the optical transmitter if a binary digital modulation signal is supplied to the optical transmitter and creating a modulated optical output signal of the optical transmitter corresponding to the binary digital modulation signal supplied to the optical transmitter. The modulated optical output signal is optically filtered in such a way that at least a portion of the optical power spectrum of the modulated optical output signal caused by a selected one of the first and second optical modes is suppressed or at least substantially attenuated.

Abstract: The invention relates to a method for creating a control channel in an optical transmission signal, wherein the optical transmission signal (SDS,i, SUS,i) includes an optical carrier frequency component, a higher frequency modulation component carrying user information to be transported from a first end to a second end of an optical transmission link and a lower frequency modulation component carrying control information, the higher frequency modulation component realizing a user channel and the lower frequency modulation component realizing the control channel, and wherein the lower frequency modulation component is created by amplitude modulation. According to the invention, the lower frequency modulation component includes a binary digital pilot tone signal component which corresponds to a pilot tone signal having a predetermined pilot tone frequency (fi).

Abstract: The invention relates to an optical WDM transmission network including at least one optical line terminal, a remote node and a plurality of optical network units. The at least one optical line terminal is connected to the optical remote node via an optical WDM path. Each optical network unit is connected to the optical remote node via an optical distribution path.

Abstract: A method for creating an optical transmit signal includes creating an electrical discrete multi-tone signal according to digital input data carrying the information to be transmitted, the discrete multi-tone signal having a plurality of electrical partial signals, each electrical partial signal defining a sub-channel. Each electrical partial signal includes a sub-carrier at a predetermined sub-carrier frequency which is modulated according to a dedicated modulation scheme, so that a dedicated portion of the digital input data is included in each sub-channel. The method includes creating an optical signal by using the electrical discrete multi-tone signal as modulating signal for amplitude-modulating the intensity of an optical carrier signal. The method further includes bandpass-filtering the optical signal in order to create an optical single sideband or vestigial sideband transmit signal.

Abstract: The invention relates to an optical WDM transmission network including at least one optical line terminal, a remote node and a plurality of optical network units. The at least one optical line terminal is connected to the optical remote node via an optical WDM path. Each optical network unit is connected to the optical remote node via an optical distribution path.

Abstract: A method for tuning a tunable optical transmitter to a target wavelength includes applying at least one tuning signal to the tunable optical transmitter to control the tunable optical transmitter to create an optical calibration signal according to nominal tuning information for the tunable optical transmitter. The optical calibration signal has a wavelength lying within a secure wavelength range, and the nominal tuning information is based on a nominal wavelength dependency for the tunable optical transmitter. The method also includes measuring a deviation between an actual wavelength dependency of the tunable optical transmitter and the nominal wavelength dependency, and determining calibration information based on that deviation. The calibration information is applied to determine a corrected nominal wavelength dependency from which target tuning information is determined. The tunable optical transmitter is controlled to create an optical channel signal according to the target tuning information.

Abstract: The invention relates to a method for creating a control channel in an optical transmission signal, wherein the optical transmission signal (SDS,i, SUS,i) includes an optical carrier frequency component, a higher frequency modulation component carrying user information to be transported from a first end to a second end of an optical transmission link and a lower frequency modulation component carrying control information, the higher frequency modulation component realizing a user channel and the lower frequency modulation component realizing the control channel, and wherein the lower frequency modulation component is created by amplitude modulation. According to the invention, the lower frequency modulation component includes a binary digital pilot tone signal component which corresponds to a pilot tone signal having a predetermined pilot tone frequency (fi).

Abstract: Disclosed is a method for transmitting a low-frequency signal over a data transmission link using a digital high bit-rate signal including the steps of creating a modulated digital high bit-rate signal the average power of which varies according to the low-frequency signal, supplying the modulated digital high bit-rate signal to a first end of the data transmission link, receiving the modulated digital high bit-rate signal at a second end of the data transmission link or at an intermediate node of the data transmission link, and detecting the low-frequency signal by low-pass filtering the received modulated digital high bit-rate signal. According to the invention, the variation of the average power of the modulated digital high bit-rate signal is effected by a variation of the density of “high” bits according to the low-frequency signal.

Abstract: A first and second head-end terminal and at least one optical add/drop filter device are connected to form a transmission path. Each head-end terminal is connected through an optical fiber to a western or eastern WDM port of an adjacent optical add/drop filter device, and each optical add/drop filter device is connected, at an eastern or western WDM port, to a western or eastern WDM port of an adjacent optical add/drop filter device. At least one tail-end terminal is connected to each optical add/drop filter device, wherein a first and second channel port of the respective add/drop tail-end terminal is connected to a dedicated first and second channel port of the optical add/drop filter device through a respective optical fiber. The head-end terminals, the optical add/drop filter devices, and the tail-end terminals are adapted to establish bidirectional communication between each tail-end terminal and the first and second head-end terminal.

Abstract: An optical WDM transmission system including a plurality of first optical transceivers at a first end of an optical WDM transmission link, each including a tunable optical transmitter being adapted to create a first digital optical channel signal within the bandwidths of a set of first optical channels of the system according to tuning control information. The first channels are multiplexed in to a first WDM signal and supplied at the first end of the WDM link. Second optical transceivers at a second end link each include a transmitter adapted to create a second digital optical channel signal within a channel bandwidth of a second set of optical channels of the system. The second channels are multiplexed into a second WDM signal for transmission to the first transceivers, and demultiplexing there.

Abstract: A method for bi-directionally transmitting digital optical signals over an optical transmission link in which a first optical transmit signal is created according to a first binary digital signal in such a way that the bit information of the first binary digital signal is included in first sections of the symbol interval of the first optical transmit signal. A second optical transmit signal is created by creating an optical wavelength reuse signal using the first optical transmit signal received at the second end of the optical transmission link, the optical wavelength reuse signal being modulated according to a second digital signal in such a way that the bit information of the second digital signal is included in second sections of the symbol interval of the first optical transmit signal received.

Abstract: An optical transmission system method including generating for a tunable laser a pilot tone having an adjustable pilot tone frequency identifying a wavelength division multiplexing channel used by the tunable laser; multiplying the pilot tone with pilot tone data to provide a pilot tone data signal; supplying the pilot tone data signal and a high frequency data signal to the tunable laser generating an optical laser signal output by the tunable laser responsive to the supplied signals; transporting the optical laser signal to a central wavelength to locker; converting the received optical laser signal to provide a pilot tone data signal for wavelength division multiplexing channels demodulated to detect the pilot tone and the pilot tone data for each individual wavelength division multiplexing channel; and identifying the wavelength division multiplexing channel on the basis of the pilot tone frequency of the detected pilot tone and evaluating the pilot tone data.

Abstract: Arrangement for transmitting an optical digital WDM signal over an optical transmission link or a passive optical network, the signal (SWDM) including N optical channels matching a given optical frequency grid. The scheme includes supplying the WDM signal (SWDM) to a near end of the optical transmission link or a near end of the passive optical network; receiving the WDM signal (SWDM) at a far end of the optical transmission link or at one or more far ends of the passive optical network; separating the optical channel signals (si(t)) by splitting and bandpass filtering the WDM signal (SWDM) received; and converting the optical channel signals (si(t)) into electrical channel signals using direct optical detection. The signal (SWDM) is created such that neighboring channel signals (si(t)) are orthogonally polarized and are conditioned with specific pre-distortion.

Abstract: A method for transmitting a binary digital transmit signal over an optical transmission link includes creating a differential optical duobinary signal, supplying the differential optical duobinary signal to a first end of the optical transmission link, transmitting the differential optical duobinary signal to a second end of the optical transmission link, and receiving the differential optical duobinary signal as a receive signal at the second end of the optical transmission link. The differential optical duobinary signal may be created by pre-coding the binary digital transmit signal having a given bit interval (T) in two pre-coding steps each with a signal delay of a single bit interval or in a single pre-coding step with a signal delay of twice the bit interval. In each case the pre-coding applies a non-XOR or equivalent operation.

Abstract: A method for tuning a tunable optical transmitter to a target wavelength includes applying at least one tuning signal to the tunable optical transmitter to control the tunable optical transmitter to create an optical calibration signal according to nominal tuning information for the tunable optical transmitter. The optical calibration signal has a wavelength lying within a secure wavelength range, and the nominal tuning information is based on a nominal wavelength dependency for the tunable optical transmitter. The method also includes measuring a deviation between an actual wavelength dependency of the tunable optical transmitter and the nominal wavelength dependency, and determining calibration information based on that deviation. The calibration information is applied to determine a corrected nominal wavelength dependency from which target tuning information is determined. The tunable optical transmitter is controlled to create an optical channel signal according to the target tuning information.

Abstract: An optical frequency locking method tunes each of a plurality of narrow-band optical channel transmit signals (having arbitrary channel frequency spacings) to a dedicated optical channel frequency. The method includes tapping-off a portion of the optical power of the respective channel transmit signal and filtering the tapped-off channel transmit signal using at least one optical filter device. The method also includes monitoring, as an optical input signal, the optical power of the respective channel transmit signal supplied to the at least one optical filter device and, as an optical output signal, the optical power of the filtered channel transmit signal. The method further includes tuning, within a predetermined locking range for the dedicated optical channel frequency, the optical frequency of the respective channel transmit signal such that a predetermined value for the ratio of the output signal and the input signal is reached.

Abstract: The invention relates to a method for monitoring a detachable fiber-optic connection, especially in a fiber-optic transmission device or system, comprising the steps of transmitting a wanted optical transmission signal carrying information data to be transmitted to at least one fiber-optic connection, a predetermined portion of the power of said optical transmission signal being reflected at the at least one fiber-optic connection depending on the status and properties of the at least one fiber-optic connection, creating a detection signal by detecting said reflected predetermined portion of the power of said optical transmission signal, monitoring and evaluating the detection signal as a function of time and creating a “DETECT” signal if the detection signal or a signal derived from the detection signal reveals a characteristic change in its course in time. Further, the invention relates to a corresponding device adapted to realize this method.

Abstract: The invention relates to a method for transmitting a binary digital transmit signal over an optical transmission link. The method includes the steps of creating a differential optical duobinary signal (SdODB(t)), supplying the differential optical duobinary signal SdODB(t)) to a first end of the optical transmission link, transmitting the differential optical duobinary signal SdODB(t)) to a second end of the optical transmission link, and receiving the differential optical duobinary signal SdODB(t)) as receive signal (SRX(t)) at the second end of the optical transmission link by detecting the optical power of the differential optical duobinary signal SdODB(t)) and creating a binary digital receive signal (SbRX(t)) corresponding to the binary digital transmit signal (SbTX(t)) by decoding the receive signal (SRX(t)).