| 摘要 |
A dual-ring, bi-directional optical fiber transmission system interconnects a series of add/drop nodes with a hub, such that multiple, widely spaced coarse wavelength division multiplexed (C-WDM) channels are established on each ring. At each node, an optical add/drop module (OADM) includes broadband filters (BBF's), such as dielectric thin film filters, arranged to (a) extract, for the purposes of a receiver, or (b) insert, for the purposes of a transmitter, information in one or more of the channels. The signals in the one or more channels are coupled to the OADM's by a standard optical transceiver, which performs modulation and demodulation. Each filter passband can be populated with multiple dense wavelength division multiplexed (D-WDM) channels, so that the capacity of traffic that can be handled at each node can be easily upgraded. The transceiver is, in turn, coupled to packet framer, such as an IP packet over SONET framer, which supplies received packets to, and receives outgoing packets from, a conventional Layer 3 routing engine. While in most instances, endpoints at each of the nodes communicate with other endpoints connected to the hub, if desired, endpoints at one or more nodes can communicate directly with endpoints on other nodes, using a direct or bypass connection through the hub. The bypass can be "permanent" or controlled via a switch, such as a micro-electro-mechanical switch (MEMS).
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