Alcatel N.v.

Ingrid Zulma Van De Voorde

Gert Van Der Plas

Denis J Mestdagh

Willem J Verbiest

Christiaan H Sierens

Jan Lieven Bert De Groote

The method is used in an optical transmission network with a plurality of terminal stations (TS1-TSn) connected to a central station (CS) via a tree-like connection structure, to determine a signal transmission delay time between one terminal station (TSi) and the central station. The terminal stations are adapted to send cells containing information signals to the central station in dedicated time slots. The method consists of sending a start signal (start CR) from the central station to the terminal station (TSi), after a first predetermined time interval after the receipt of that start signal sending a ranging signal from the terminal station to the central station, after a second predetermined time interval after the sending of the start signal sending an inhibit signal from the central station to the terminal stations to indicate that no cells may be transmitted during an idle time window; determining in the central station the signal transmission delay time from the contents of the predetermined ranging signal received by the central station during the idle time window. The ranging signal either has an amplitude which is smaller than the information signals contained in the cells in order not to disturb the information signals when the ranging signal is transmitted outside the idle time window, or has a similar amplitude, in which case error codes are included in the cells in order to recover possible disrupted cells.

Method for measuring a signal transmission delay time, central station,

The optical amplifier combiner arrangement is used in a tree-like optical network (APON) comprising a cascade connection of dedicated branches, of the arrangement and of a common branch. The arrangement is coupled between a plurality of optical network users and an optical line terminator, via the dedicated branches and the common branch respectively. The network enables upstream transmission of information signals from the optical network users to the optical line terminator. The optical amplifier combiner arrangement includes for each branch of the dedicated branches (1) an optical amplifier to amplify an information signal with a gain value and to thereby generate an amplified information signal with a predetermined power level, (2) an optical on/off switch coupled between the optical amplifier and an optical combiner to pass the amplified information signal when the information signal is present and to interrupt the branch when the information signal is not present. The optical combiner is included in the arrangement to combine all amplified information signals according to a multiple access technique and to thereby generate an outgoing optical signal for application to the optical line terminator.

Optical amplifier combiner arrangement and method for upstream

The system includes two transmitters (T1, T2) and two receivers (R1, R2). One transmitter (T1) may include a wavelength tunable laser, sending an FSK optical signal (OS1) which has a constant intensity. In a first receiver (R1) this FSK optical signal (OS1) is transformed into an IM signal (OS1') by an optical pass band filter. This IM signal (OS1') is then detected by a first direct detection receiver (DM). In a second direct detection receiver (R2) the FSK optical signal (OS1) is not detected, since it has constant intensity. A second transmitter (T2) includes a Fabry Perot laser or a LED with a broad linewidth, sending an IM optical signal (OS2). This IM optical signal (OS2) is detected by the second direct detection receiver (R2). It is not detected by the first direct detection receiver (DM), because it is strongly attenuated when passing through the narrow bandpass optical filter (TM) before being applied to the first direct detection receiver. This system is especially advantageous in bidirectional optical transmission systems, due to its inherent insensitivity to reflections.

Optical transmission system

A protection arrangement protects an optical transmitter device with n optical transmit circuits or an optical receiver device with n optical receive circuits. It includes fault evaluating circuitry to detect a defective transmit/receive circuit, a spare transmit/receive circuit, and switching circuitry. Upon detection of a defective transmit/receive circuit by the fault evaluating circuitry, the fault evaluation circuitry controls the spare transmit/receive circuit and the switching circuitry to bypass the defective transmit/receive circuit with the spare transmit/receive circuit.

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Wilrijk, Belgium

Ingrid Zulma Van De Voorde