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Interface Specifications
Interface Specifications
The physical layer interface for the PA-POS-1OC3 is Optical Carrier-3 (OC-3c), the specification for
SONET STS-3c and SDH STM-1 transmission rates, and the PA-POS-1OC3 is designed to comply with
Packet-over-SONET specifications. The PA-POS-1OC3 provides one 155.520-Mbps packet OC-3
network interface for all supported platforms.
The PA-POS-1OC3 has a duplex LC-type receptacle that allows connection to single-mode or multimode
optical fiber. (For more information on the optical fiber cables you should use with this port adapter, see
the
Packet data is transported using Point-to-Point Protocol (PPP) and is mapped into the STS-3c/STM-1
frame. The encapsulations used add approximately half the number of bytes of transport overhead as that
involved with ATM using ATM Adaptation Layer 5 (AAL5) and line card control (LCC) Subnetwork
Access Protocol (SNAP) encapsulations.
The PA-POS-1OC3 interface is compliant with RFC 1619, PPP over SONET/SDH, and RFC 1662, PPP
in HDLC-like Framing. The PA-POS-1OC3 supports RFC 1619 PPP over SONET/SDH encapsulation,
and provides support for SNMP agent v1 (RFC 1155–1157), and Management Information Base (MIB)
II (RFC 1213).
OC-3 Optical Fiber Specifications
The OC-3 specification for optical fiber transmission defines two types of fiber: single-mode and
multimode. Within the single-mode category, two types of transmission are defined: intermediate reach
and long reach. Within the multimode category, only short reach is available.
Modes can be thought of as bundles of light rays entering the fiber at a particular angle. Single-mode
fiber allows only one mode of light to propagate through the fiber, and multimode fiber allows multiple
modes of light to propagate through the fiber.
Multiple modes of light propagating through the fiber travel different distances depending on the entry
angles, which causes them to arrive at the destination at different times (a phenomenon called modal
dispersion); therefore, single-mode fiber is capable of higher bandwidth and greater cable run distances
than multimode fiber.
optical fiber transmission.
If the distance between two connected stations is greater than the maximum distances listed, significant
Note
signal loss can result, making transmission unreliable.
PA-POS-1OC3 Single-Port Port Adapter Installation and Configuration Guide
1-4
"Cables and Connectors" section on page
Table 1-1
1-7.)
lists nominal OC-3 optical parameters for single-mode and multimode
Chapter 1
PA-POS-1OC3 Overview
OL-6514-04
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