This invention relates generally to the field of telecommunications and routing signals over optical fibers. More particularly, this invention relates to the effective routing of multiple optical signals having diversity requirements from one or more other optical signals.
Optical networks are designed to transmit signals, such as voice and/or data signals, over fiber optic cables from one point to another. The optical networks include multiple optical transport systems (OTSs) and terminal offices. Each OTS includes fiber optic cables connecting two end terminals, such as dense wavelength division multiplexing units (DWDMUs), also referred to as termination points or nodes. Each OTS may also include other electronic devices such as optical amplifiers.
An optical network typically includes equipment provided by different vendors. Synchronous optical network (SONET) defines an optical interface standard that enables the compatability of transmission products from various vendors. The interface standard governs rates and protocols for successful signal transmission, such as optical lines rates, also known as optical carrier (OCn) rates, frame format, and operations, administration, maintenance and provisioning protocols.
Over the past decade, many telecommunication companies have been utilizing SONET rings in their networks. SONET rings connect the optical transport systems in a ring. Typically four or five nodes are connected to each SONET ring, although a different number of nodes could be used. The SONET ring architecture uses, at a minimum, a four-wire arrangement. Two of the fibers are referred to as service fibers and are uni-directionally oriented in opposite directions from one another. In other words, a first service fiber is used for transmitting a signal from point A to point B and a second service fiber is used for transmitting a signal from point B to point A. The remaining two fibers are referred to as protection fibers. The protection fibers are oriented in the same fashion as the service fibers. SONET rings are typically built with “smart” devices such that if the fibers on part of the ring are no longer capable of transmitting signals, the signals are transferred to functional fibers located on a different section of the ring for transmission.
Current data transmissions can have less stringent restoration requirements than voice transmissions. In the past, for voice applications, telecommunication networks used both service and protection fibers to minimize noticeable transmission delay. For data applications, some transmission delay is often acceptable to the users. For example, if a network is being used to transmit an electronic message from one user to another, a delay for restoration of the network might not be objectionable to users, as it would be in voice transmission. For data applications, users might be willing to obtain “unprotected” service from a telecommunications company at a reduced cost in comparison to “protected” service.
However, data transmissions may have more stringent diversity requirements than voice transmissions. Users, such as Internet Service Providers (ISPs), will often require the transmission of signals over a great distance, such as across the United States. Given that users will accept some delay in data transmission, to improve the likelihood of a successful transmission, a user might require multiple transmission routes so that if one route has a link that is down, signals may then be transmitted over a different route. However, it is possible that multiple transmission routes have some fiber spans in common. If all the transmission routes share common fibers that fail, then all of the transmission routes will go down. To avoid this occurrence, a user might request that the transmission routes be diverse from one another; that is, that the routes do not share common fiber spans.
In addition to the need for diversity, there is also a need for sufficient capacity. As traffic, i.e., the amount of signals being transmitted through a network increases, there exists a need to increase capacity to accommodate the increased traffic, or to re-route the traffic to less congested routes.
Given the foregoing, there is a need for identifying transmission routes that satisfy the diversity and capacity requirements of the users.