Optical communications – Diagnostic testing – Fault detection
Reexamination Certificate
2000-01-07
2003-07-29
Pascal, Leslie (Department: 2733)
Optical communications
Diagnostic testing
Fault detection
C398S022000, C398S143000, C398S144000, C398S167000, C398S178000
Reexamination Certificate
active
06599038
ABSTRACT:
TECHNICAL FIELD
This invention relates to remote management and monitoring of fiber optic circuits and, in particular, to a method and apparatus for enabling remote monitoring of a fiber optic circuit that terminates on the apparatus.
BACKGROUND OF THE INVENTION
The use of fiber optics as a signal distribution medium is becoming increasingly popular. This is due to several factors. Fiber offers by far the greatest bandwidth of any transmission system. Since fiber is dielectric, it is not susceptible to radio or electromotive interference. Neither does it emit radio or electromotive interference. Although light signals suffer from attenuation, they are less prone to attenuate than electrical signals on a copper medium. Fiber is also intrinsically secure, because it is virtually impossible to place a physical tap without detection. Since no light is radiated outside a fiber optic's cable, physical taps are the only means of signal interception. For all these reasons, the use of fiber optic delivery systems is becoming ubiquitous.
Optical fibers are of two basic types, multi-mode and single mode. Multi-mode fiber is less expensive to produce, but has lower performance than single mode fiber because the inner core is larger in diameter. As the light rays travel down a Multi-node fiber, they disperse due to a phenomenon known as modal dispersion. Although reflected back into the inner core by the cladding on the fiber strands, different light rays travel different distances and therefore arrive at different times. As a length of the circuit increases and the speed of transmission increases, the pulses of light tend to interfere with each other in a phenomenon known as pulse dispersion. At that point, the light detector is unable to distinguish between the individual pulses. As a result, multi-mode fiber is generally used in applications involving relatively short distances and lower speeds, such as within customer premises.
Single mode fiber has a thinner inner core. It therefore performs better than multi-mode fiber over longer distances and at higher transmission rates. Although more expensive to manufacture, single mode fiber is used in long distance transmission links and particularly in high bandwidth applications.
Carriers typically use single mode fiber for fiber circuits to deliver services to customer premises. Customers typically use multi-mode fiber because it is less expensive and normally adequate for service delivery within the restricted environment of the customer premises. An interface is required at the customer demarcation point to convert from single mode to multi-mode signals. Such interfaces are well known in the art. A problem frequently experienced with such interfaces is that faults are difficult to isolate. When a communications fault is reported to a service provider, the service provider frequently has no choice but to dispatch a customer service representative to isolate the problem. There therefore exists a need for an apparatus adapted to terminate a fiber circuit that is capable of self-monitoring as well as being capable of entering a command mode that permits remote testing of the fiber circuit by providing a loop-back function to enable the fiber circuit to be monitored by sending a signal to the apparatus and checking to determine whether the same signal is received from the apparatus.
There is also a need for an apparatus that is secure, to ensure that unauthorized individuals cannot assume control or influence the operation of the fiber optic circuit.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide an apparatus for enabling remote testing of a fiber optic circuit between a first end point and the apparatus.
It is a further object of the invention to provide an optical repeater that is adapted to enable testing of fiber optic circuits to which it is connected.
The invention therefore provides an apparatus that enables remote testing of a fiber optic circuit between a first end point and the apparatus, and a second fiber optic circuit between the apparatus and a second end point. The apparatus comprises a first transceiver for terminating the first fiber optic circuit between the first end point and the apparatus, and a second transceiver for terminating the second fiber optic circuit between the apparatus and the second end point. The apparatus also includes a high speed multiplexer that interconnects the first and second transceivers. A control unit of the apparatus controls the high speed multiplexer and automatically monitors other predetermined functions of the apparatus. The apparatus also includes at least one communications port for remotely communicating with the control unit to permit a remote administrator to perform remote testing of the fiber circuit and to monitor the other predetermined functions of the apparatus.
Typically, the first end point for the first fiber optic circuit is a service provider's equipment, and the second end point is a customer premise equipment, a local area network (LAN), for example. The first and second end points may also be repeaters in a fiber optic link.
The first and second fiber optic circuits may operate in different transmission modes. Typically, the first fiber optic circuit operates in a single mode and the second fiber optic circuit operates in a multi-mode. The apparatus in accordance with the invention is adapted to automatically convert from one mode to the other, and vice versa.
The apparatus in accordance with the invention is also adapted to control the high speed multiplexer on command, to loop-back signals received by either the first and second transceivers. This permits a remote administrator to test the integrity of a fiber optic circuit by commanding the transceiver to loop-back a signal sent from one of the first and second ends and monitoring receipt of the same signal. If the looped-back signal is received, the fiber optic circuit is determined to be operational without dispatching service personnel.
Command control of the apparatus is effected through at least one telecommunications port. Preferably, a telephone modem interface and a data interface are both provided. Access through each interface is strictly controlled by programmed procedures that only accept communications sessions from selected addresses. Any attempt to establish a communications session from any other address raises an alarm. Preferably, the alarm is automatically reported by the apparatus, which establishes a communications session with a predetermined address to report the alarm. The communications session is preferably established through the Public switched Telephone Network (PSTN) using the telephone modem interface.
The invention also provides a method of monitoring a remote apparatus for providing a connection between first and second fiber optic circuits, the remote apparatus converting optical signals received from either of the first and second fiber optic circuits into electrical signals and converting the electrical signals back into optical signals sent through an appropriate one of the first and second fiber optic circuits. The apparatus includes a control unit for monitoring functions of the apparatus. In accordance with the method, the apparatus automatically cyclically monitors predetermined functions of the apparatus to determine whether each of the predetermined functions are operating within a predetermined range. If the apparatus determines that any one of the functions is not operating within the predetermined range, the apparatus raises an alarm. The apparatus preferably determines whether the alarm is an alarm to be reported. It the alarm is an alarm to be reported, the apparatus automatically establishes a communications session with a predetermined alarm report address and automatically reports the alarm. In accordance with a preferred embodiment of the invention, every alarm is an alarm to be reported.
Preferably, the apparatus in accordance with the invention monitors at least: a) carrier on the first fiber optic circuit; b) carrier on the
Pascal Leslie
Priority Electronics Inc.
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