Positionally independent application of an OTDR technique based on correlation in a branched optical fibre network during operation

• US 5,570,217 A
• Filed: 10/28/1994
• Issued: 10/29/1996
• Est. Priority Date: 11/04/1993
• Status: Expired due to Fees

• Current Assignee: Koninklijke Philips N.V.
• Original Assignee: Koninklijke Philips N.V.
• Inventors: Fleuren, Franciscus H.
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): BACARES, RAFAEL D
• Application Number:
  US08/331,221
• Time in Patent Office: 732 Days
• Field of Search: 359/110, 359/173, 359/154, 356/73.1, 250/227.15, 250/227.14, 385/15
• US Class Current: 398/13
• CPC Class Codes: H04B 10/07 Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
• CPC Class Codes: H04B 10/071 using a reflected signal, e.g. using optical time domain reflectometers [OTDR]

Abstract

In a branched optical fibre network in which an optical signal (I) modulated with a data signal is distributed by a transmitter connected to the network, OTDR based on correlation is applied independently of position by uncoupling both a signal part (I₁) of the distributed signal (I) in the forward direction and a signal part (R₁) of the reflected signal (R) in the return direction at an arbitrarily chosen uncoupling point P in a fibre connection (46) of the network, detecting them and correlating them with one another. A device for performing such a positionally independent correlation OTDR is provided with uncoupling means (60) having a first signal output (68) and a second signal output (66), via which outputs the signal part (I₁) and the signal part (R₁), respectively, are fed to optical receivers (70 and 71). The signal parts received are detected by the receivers, demodulated and corresponding electrical signals are supplied to a correlator (78) which produces an OTDR signal for an OTDR imaging means (82).

Claims

1. A method of monitoring, by means of fault location with the aid of optical time-domain reflectometry based on correlation, at least a part of an optical fiber transmission network comprising at least one optical fibre connection for distributing an optical signal, modulated with a data signal, from a transmitter connected to the optical transmission network to at least one receiver, the method comprising the steps of:

a first uncoupling step of uncoupling a first optical signal from the network at an uncoupling point in a fiber connection of the network ahead of said part of the network, said first optical signal being a fraction of the distributed optical signal;

a second uncoupling step of uncoupling a second optical signal from the network at or near the uncoupling point, said second optical signal being at least a fraction of signals reflected in said part of the network being monitored;

a converting step converting separately said first and second optical signals to first and second electrical signals, respectively, and

a correlating step of correlating said second electrical signal with said first electrical signal.

2. The method according to claim 1, wherein at least one of the first and second uncoupling steps is performed using uncoupling means which can be coupled to said optical fiber connection at the position of said uncoupling point.

3. The method according to claim 1, wherein the first and second uncoupling steps are performed with uncoupling means incorporated in the optical fibre connection at the position of said uncoupling point.

4. The method according to claim 3, further comprising the step of amplifying the distributed optical signal prior to the uncoupling of the first optical signal.

5. A device for monitoring, by means of fault location with the aid of optical time-domain reflectometry based on correlation, at least a part of an optical transmission network comprising at least one optical fibre connection for distributing an optical signal, modulated with a data signal, from a transmitter connected to the optical transmission network to at least one receiver, the device comprising:

a first uncoupling means for uncoupling a first optical signal from the network at an uncoupling point in a fiber connection of the network ahead of said part of the network, said first optical signal being a fraction of the distributed optical signal;

a second uncoupling means for uncoupling the second optical signal from the network at or near the uncoupling point, said second optical signal being at least a fraction of signals reflected in said part of the network being monitored;

first and second photo/electrical conversion means for separately converting said first and second optical signals to first and second electrical signals, respectively; and

correlation means for correlating the second electrical signal with the first electrical signal and for supplying a signal for optical time-domain reflectometry in that part of the optical transmission network which is to be monitored.

6. The device according to claim 5, wherein at least one of the first and second uncoupling means can be coupled.

7. The device according to claim 6, wherein said at least one of the first and second uncoupling means is a coupler of the `clip-on` type.

8. The device according to claim 7, wherein each of the first and second uncoupling means is a coupler of the `clip-on` type.

9. A device for monitoring by means of fault location with the aid of optical time-domain reflectometry based on correlation, at least a part of an optical transmission medium comprising at least one optical fibre connection for distributing an optical signal, modulated with a data signal, of a transmitter connected to the optical transmission medium to at least one receiver, the device comprising:

optical uncoupling means provided with a first optical signal output and a second optical signal output, respectively, for coupling at least a fraction of the optical modulated signal and at least a fraction of the reflected signal out of a fibre connection in the optical transmission medium;

first signal derivation means for deriving a first signal corresponding to the modulated optical signal transmitted in the direction of the at least one receiver;

second signal derivation means for deriving a second signal corresponding to a signal reflected in that part of the optical transmission medium which is to be monitored, the first and the second signal derivation means including opto/electrical converters coupled, respectively, to the first and the second signal output of the uncoupling means;

correlation means for correlating the second signal with the first signal and for supplying a signal for optical time-domain reflectometry in that part of the optical transmission medium which is to be monitored;

wherein the uncoupling means comprise a combined coupler/splitter provided with two input ports and two output ports, of which a first input port forms the first optical signal output and a first output port forms the second optical signal output, and the second input port and the second output port can be connected to fibre ends of a fibre connection which is opened at the selected uncoupling point.

10. The device according to claim 9, wherein the second input port includes an optical amplifier.