Optical communications – Diagnostic testing – Fault location
Reexamination Certificate
2001-01-11
2004-08-17
Negash, Kinfe-Michael (Department: 2633)
Optical communications
Diagnostic testing
Fault location
C398S010000, C398S009000, C398S016000, C398S017000, C398S079000, C379S029010
Reexamination Certificate
active
06778778
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to an arrangement and method for testing telecommunications circuits over Dense Wavelength Division Multiplexing (DWDM). Yet more particularly, the present invention relates to an arrangement and method that enable testing of cross country circuits over DWDM by a single person.
As is known, telecommunication service providers have created cross country or ultra-long haul networks. These networks are driven, in part, by the nature of internet and data traffic and by ever expansive enterprise networks. Voice traffic, on the other hand, is characterized as more regional and served principally by metropolitan and regional networks. Network planners visually depict these two developing traffic patterns as network overlays, served by different transmission equipment. Internet and data traffic over these networks has been increasing at a significant rate and currently dominates voice traffic for many long distance service providers.
Telecommunication service providers continually look toward new technologies leading to greater network carrying capacity, or bandwidth, and increasing transmission distances, which are the length separations between system transmitting and receiving terminals. DWDM is the favored optical technology for increasing bandwidth on an optical fiber. DWDM operates by multiplexing and transmitting a number of signals, i.e. OC-48 or OC-192, simultaneously at different wavelengths on the same optical fiber. As a result, a single optical fiber provides a number of virtual optical fibers by carrying a number of simultaneous signals. This permits greater network traffic through increased bandwidth.
The most aggressive service providers have deployed 40 channel DWDM systems with transmission distances limited to around 500 km before requiring Optical-Electrical-Optical (O-E-O) regeneration of the optical bit streams. Thus, DWDM systems are connected back-to-back for cross country connectivity. In order to overcome these limitations, DWDM system manufacturers are presently offering to at least double both channel count and transmission distance. More elaborate technologies will lead to greater length/bandwidth products and true ultra-long haul systems.
Along with the interests aimed at increasing both transmission length and bandwidth, a greater importance is being placed on developing more efficient network management tools and test equipment. Service providers have been instrumental in driving this development and embedding performance measures and diagnostic tools into their system elements. Circuit tests that are performed by field operators include, for example, tests for optical power levels, loss of signal modulation, and code violations.
Currently, field technicians cannot trouble-shoot an entire cross country DWDM circuit without tremendous group coordination. Each cross country DWDM circuit comprises a number of sub-circuits that must be administered by a local field technician during a test. For example, a circuit from State 1, which is located in one region of a country, to State 4, which is located in a distant region of the country, might comprise multiple, sequential sub-circuits from State 1 to State 2, State 2 to State 3, and State 3 to State 4. During a test, a local field technician for a sub-circuit can only monitor and trouble-shoot their individual sub-circuit. Therefore, to obtain information relating to another sub-circuit, a field technician must either communicate with another field technician who is monitoring the other sub-circuit or rely on personnel in a Network Operation Center (NOC) that can survey the entire circuit.
Less reliance on the NOC is desired. It is impractical for a NOC to be heavily involved in turn-up testing or prolonged maintenance tasks. A NOC should rather be focused on in-service traffic management.
It is therefore desirable to empower field operations by providing the tools and test equipment needed for a network to efficiently manage turn-up and maintenance requirements.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an arrangement and a method for testing that 1) reduces the cost of test equipment and 2) consumes less time and manpower than known arrangements and methods.
The present disclosure provides one or more embodiments directed to improvements in testing fiber optic telecommunications circuits over DWDM. These improvements can be provided in a single all-encompassing unit or practiced separately.
To this end, in one embodiment, there is provided a method for testing a circuit over Dense Wavelength Division Multiplexing (DWDM). A test-drive signal is transmitted on the circuit and a performance of the circuit is monitored at points along the circuit based on the transmitted test-drive signal.
In an embodiment, the field technician accesses downstream Network Elements (NE) over an Operations Support System (OSS) Network. The OSS Net is accessed via a LAN connection or via a dial-up connection and providing login information. For example, a field technician may Telnet to a downstream NE and provide the necessary login information to bring up that NE's management system or Craft Interface as if being on site and physically connected to the NE. Performance measures are visible at the Craft Interface display screen. As a result, the present invention enables testing of cross country circuits over DWDM by a single person.
In another embodiment, there is provided an arrangement for testing a telecommunications circuit over Dense Wavelength Division Multiplexing (DWDM). The arrangement comprises a transmitter for transmitting a test-drive signal on the circuit, which is optically coupled to a near end of the circuit. A network monitors performance of the circuit at points along the circuit based on the transmitted test-drive signal. As a result, the present invention provides an arrangement for testing an entire cross country circuit that requires only a single transmitter. A single field operator, who operates the transmitter, also monitors performance of any point on the circuit as described above. Other field operators can also monitor the circuit from their locations.
A DWDM circuit can comprise a number of sub-circuits, each sub-circuit having terminals at each end and possibly having at least one optical add-drop multiplexer and/or optical line amplifier. The performance of the circuit is monitored via the network at at least one of a number of network elements along the circuit. Network elements comprise, for example, optical add-drop multiplexers and optical line amplifiers.
In another embodiment, there is provided a display, such as a laptop computer or Craft Interface Device (CID), which is connected to the network for displaying the monitored performance of the circuit. The display device can be connected to the wide area network via one of a local area network or dial-up connection.
In another embodiment, the transmitter is similarly controlled via the OSS Net or by direct physical connection using the same display device or CID or by a separate display device or CID.
The present invention is applicable to any transport framing structure with system support for “in-band” signaling and detection of key performance measures. For example, in an embodiment, SONET and SDH signals are transported over a DWDM system with performance monitoring at system client side ingress and egress points for optical power levels, loss of signal modulation, and code violations.
In the present discussion, IP or ATM circuits merely describe example cross country DWDM circuits; IP and ATM are traffic descriptors of the services transported within the payload area of a concatenated SONET or SDH signal. SONET and SDH provide various other channelized mixtures and payload mappings for transport of, for example, DS3, E1, or DS1 services.
These and other features of the invention will become clearer with reference to the following detailed description of the presently preferred embodiments and accompanying drawings.
REFE
Richards Douglas L.
Williams David W.
Yarkosky Francis R.
Negash Kinfe-Michael
Sprint Communications Company L.P.
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