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AssigneeNorthern Telecom Limited
InventorsMartin J. Pettitt, Anagnostis Hadjifotiou
Estimating the term…
An analogue telemetry system/method provides fault location in an optical transmission system including optical fibre amplifiers. Each amplifier includes an optical fibre amplifier with an AGC loop therearound, a respective optical pump source being included in the AGC loop. In the AGC loop the spontaneous emissions from the amplifier fibre is detected and employed to drive the pump source appropriately to maintain the amplifier output at a predetermined level. A supervisory tone is applied at the transmission end of the system. At each amplifier the presence of the supervisory tone or a distress tone from a previous amplifier is looked for. If either tone is detected the signal is amplified and transmitted to the next amplifier. If neither tone is detected a respective amplifier distress tone is applied to the respective optical pump source. At the receiver end of the system the supervisory tone is sought or, in its absence, a distress tone or no tone at all from this information the position of a system fault determined.
An analogue telemetry system for use with an optical transmission system including a transmitter terminal having an optical output, a plurality of concatenated optical fibre amplifiers, each having a respective optical pump source comprising a laser, and a receiver terminal, all interconnected by optical fibre, each optical fibre amplifier including an optical amplifier fibre with an automatic gain control (AGC) loop therearound, the respective optical pump source being included in the respective AGC loop, wherein in the AGC Loop spontaneous emission from the optical amplifier is detected and employed to drive the respective laser pump source appropriately to maintain the optical fibre amplifier output at a predetermined level, the telemetry system including means for applying a supervisory tone to the optical output from the transmitter terminal, means at each said optical amplifier for selectively applying to that amplifier's output a distress tone at a frequency unique to that amplifier and different from that of the supervisory tone by superimposing a respective modulation on to that amplifier's laser pump source which respective modulation is in turn transferred to the optical amplifier fibre's spontaneous emission, means at each optical fibre amplifier for detecting the presence of either the supervisory tone or a distress tone from any preceding amplifier, and amplifying the incoming signal if either of said tones is present, and wherein each optical fibre amplifier is arranged to apply its respective distress tone characteristic of that amplifier to the amplifier's output if neither of said supervisory or distress tones are present, and wherein means are provided at the receiver terminal for detecting the presence of the supervisory tone, a said distress tone or the absence of either such tones, the latter or the received distress tone serving to indicate and locate a transmission system fault.
An analogue telemetry method for use with an optical transmission system including a transmitter terminal having an optical output, a plurality of concatenated optical fibre amplifiers, each having a respective optical pump source comprising a laser, and a receiver terminal, all interconnected by optical fibre, each optical fibre amplifier including an optical amplifier fibre with an automatic gain control (AGC) Loop therearound, the respective optical pump source being included in the respective AGC loop, each said optical amplifier having means for applying a distress tone at a frequency unique to that amplifier and different from that of the supervisory tone by superimposing a respective modulation on to that amplifier's laser pump source which respective modulation is in turn transferred to the optical amplifier fibre's spontaneous emission, the method including the steps of detecting in the AGC loops spontaneous emission from the optical amplifier fibres and employing the detected spontaneous emission to drive the respective laser pump sources appropriately to maintain the optical fibre amplifiers outputs at a predetermined level, applying a supervisory tone to the optical output from the transmitter terminal, detecting, at each optical fibre amplifier, the presence of either the supervisory tone or a distress tone from any preceding amplifier, amplifying the incoming signal for transmission to the next amplifier if either of said tones is present or applying its respective distress tone characteristic of that amplifier to the amplifier's output if neither tone is present, detecting at the receiver terminal the presence of the supervisory tone, a said distress tone, or the absence of either such tones, and determining from the latter or the received distress tone the location of a transmission system fault.
Dependencies are inferred from the claim text.