Terminology » Fiber Optic » OTN Interfaces: OTU1 vs OTU2 vs OTU3 vs OTU4 Explained

OTN Interfaces: OTU1 vs OTU2 vs OTU3 vs OTU4 Explained

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This article compares OTN interfaces, specifically OTU1, OTU2, OTU3, and OTU4, highlighting the key differences between them. OTU stands for Optical Channel Transport Unit, and OTN stands for Optical Transport Network.

Introduction to OTN

  • OTN (Optical Transport Network) consists of various optical network elements connected by optical fiber lines.
  • OTNs are used to support functionalities that maintain optical links carrying client optical signals.
  • Typical OTN functions include multiplexing, transport, switching, management, supervision, and survivability.
  • OTN is defined in the ITU-T G.709 standard.
  • It employs WDM (Wavelength Division Multiplexing), unlike SDH/SONET.

OTU client signal mapping

Figure 1: OTU client signal mapping

OTU1 vs OTU2 vs OTU3 vs OTU4 Specifications

The following table outlines the specifications of OTU1, OTU2, OTU3, and OTU4.

SpecificationsOTU1OTU2OTU3OTU4
Line rate (Mbps)2.66610.70943.018111.809
Payload Rate (Mbps)2.48810.03740.150104.794
Frame period (µs)48.97112.1913.0341.167
Frequency accuracy (ppm)+/- 20+/- 20+/- 20+/- 20
ApplicationTransports SONET OC-48 or SDH STM 16.Transports OC-192, STM-64 or WAN PHY for 10GBase-W.Transports OC-768, STM-256 or 40 GB ETHERNET.Transports 100 GB ETHERNET Signal.