Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Patent
1993-04-29
1994-11-22
Chilcot, Jr., Richard E.
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
359125, 359167, 371 201, 370 13, H04B 1008
Patent
active
053673948
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to test apparatus, and, in particular, to apparatus suitable for use in conjunction with a passive optical network (PON) system.
2. Related Art
The applicant's International patent applications numbers GB 90/01758 (WO91/08623) and GB 91/00100 describe a TPON (Telephony on a Passive Optical Network) system designed to carry data via a Bit Transport System (BTS). The TPON system includes a head-end station having a time division multiple access (TDMA) master which assembles incoming exchange traffic into TDMA frames. These frames are broadcast via an optical stage onto a fibre network. Each of a number of terminations connected to the network recognizes and responds to an appropriately addressed portion of the data in the broadcast frame and ignores the remainder of the frame.
The header portion of each frame includes regions used for the monitoring and control of the system. In particular, as described in the above mentioned applications, upstream TDMA frames may include a ranging check pulse transmitted by a termination. In response to this ranging check pulse the head-end station transmits control signals to the termination to modify the timing of transmissions from the termination so as to correct for any variations in the time of receipt of the transmissions. The transmission from a termination is arranged to be delayed, with respect to the receipt of a TDMA frame, by a certain amount as determined by the head-end station such that the terminal transmission is in its correct place in the upstream TDMA frame received at the head-end station. The head-end station is typically arranged to generate an alarm signal if the terminal transmission delay as measured by the receipt of the ranging pulse falls outside a predetermined range. The head-end station may also transmit a diagnostic signal onto the network, as described in our International patent application number GB 91/01815.
While monitoring and control procedures of the type outlined above are effective once the TPON system is fully installed and running they are not in themselves capable of providing all the diagnostic functions necessary for a termination whilst that termination is being installed. Moreover those diagnostic functions which can be carried out provide an output in the form of alarm signals or other indications of the state of the network only at the head-end station. The relevant information is not then available directly for use by, for example, an engineer installing a termination at a position remote from the head-end station.
BRIEF SUMMARY OF THE INVENTION
According to the present invention there is provided a test apparatus for use with a PON system comprising a head-end station connected via a fibre optic network to a plurality of terminations, each termination being arranged to carry out self-diagnostic procedures and to generate status signals for transmission to the head-end station, the apparatus being characterised by means for data communication with a said termination, first detection means arranged to detect, in use, status signals generated by the termination, second detection means arranged to detect, in use, alarm signals in a data frame transmitted from the head-end station via the fibre optic network and received at the termination, and indication means responsive to the first and second detection means to provide an output indicative of the condition of the termination.
The present invention provides a test apparatus capable of carrying out local diagnostic tests on a termination, and also of providing local access to diagnostic procedures carried out by the head-end station. Such an apparatus greatly facilitates the work, for example, of an engineer installing a new termination by making it possible for that engineer to carry out a range of diagnostic tests on site.
In a test apparatus for use with a PON system in which the head-end station and the terminations are arranged to transmit and receive data frames comprising a plural
REFERENCES:
patent: 4516216 (1985-05-01), Armstrong
patent: 5046807 (1991-09-01), Unitt
patent: 5153764 (1992-10-01), Faulkner et al.
Patent Abstrcts of Japan, No. JP58164357, Sep. 29, 1983, Kazumi, "Title Monitoring Control System".
IEEE Global Telecommunications Conference, Globecom 85, vol. 3, No. 44.5, 4 Dec. 1985, New Orleans, Louisiana, pp. 4451-4456, D. G. Allan et al, "Design of Integrated Surveillance Systems for High Capacity Fiber Systems".
Chuter Jeremy B.
Clarke Donald E. A.
Hale Michael A.
British Telecommunications public limited company
Chilcot Jr. Richard E.
Negash K.
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