SONET & SDH optical testing

OC-3/STM-1 and OC-12/STM-4 Analysis and Emulation

SonetExpert™ Channelized (SEC) Analyzer

Multiservice test tool for next generation Synchronous Optical Networking (SONET) and Synchronous Digital Hierarchy (SDH) carrying channelized TDM (T1, E1) traffic



A majority of the backbone transport for voice, video and data applications continues to be SONET and SDH optical transmission networks. SONET and SDH transmission network also continue to be used for conventional channelized traffic – carrying many TDM T1, E1, T3, and E3 pipes.

GL's SonetExpert™ hardware platform (USB Unit) is capable of OC-3/STM-1 and OC-12/STM-4 wirespeed processing on two optical ports (Port 3 and Port 4) for channelized data carrying many independent unframed/framed T1 and E1 streams. USB 3.0 interface is used to connect with a Notebook PC for portability.  The hardware is firmware FPGA based making it easy to upgrade in the field for application versatility. A unique feature of the unit is the capability to capture, transmit and process at wirespeed to/from applications and hard disk on all interfaces.

In an OC-3/STM-1, all 84 T1s or all 63 E1s can be identified and processed in transmit and receive modes. In an OC-12/STM-4, all 336 T1s or all 252 E1s can be identified and processed in transmit and receive modes.

SonetExpert™ Channelized Analyzer comprises of hardware and software receiving and transmitting data using SONET and SDH networks and communicating with the GL Soft T1/E1 Analyzer application. Provides an essentially the same feature rich functionality as GL hardware based T1/E1 Analyzers with the difference that T1/E1 frames are multiplexed into SONET/SDH frames and transmitted over optical lines.

Main Features

  • Allows to configure the number of T1 E1 channels to be Multiplexed/Demultiplexed to / from OC-3/12 STM-1/4
  • 2 Channelized OC-3 STM-1/OC-12 STM-4 SONET/SDH interfaces per unit for simulating and monitoring both directions
  • Allows direct access to everything on SONET / SDH – Framing and Payload, including structured traffic (T1, E1, STS-1 etc)
  • Comprehensive analysis / emulation of voice, data, fax, protocol, analog, and digital signals, including echo and voice quality testing
  • Pluggable SFPs allow Single-mode (SM), and Multi-mode (MM) fiber optic non-intrusive tap
  • Comprehensive protocol analysis and emulation - HDLC, SS7, ISDN, CAS, PPP, Frame Relay, ATM and more
  • Direct access to any or all T1s and E1s
    • 2 x 336 T1’s x 24 DS0s = 16,128 DS0s
    • 2 x 252 E1’s x 31 DS0s = 15,624 DS0s
  • Scans the received STM-4/STM-1 traffic and identifies the mapping, tributary type [T1/E1], equipped/unequipped status of the tributaries
  • Broadcasts the selected T1/E1 channel data on all the 252 E1’s or 336 T1’s
  • Supports any combination of DS0/64/56/16/8 kbps fractional T1/E1, and N x T1/E1 interface definitions (a total of 252 E1s or 336 T1s – in each port)
  • Supports multiplexing multiple T1 or E1 channels to a single channelized OC-3/12 STM-1/4 line
  • User configurable OC-3/12 STM-1/4 mapping – allows user-defined T1 and E1 channels to multiplex. The channel numbering is same as in demultiplexer
  • User configurable idle code to fill the channels when the user added channels do not have data to multiplex.

SonetExpert™ Hardware Unit (Front and Back Panel)

SonetExpert™ contains 4 ports, out of which two ports (Port 3 and Port 4) are designated for SONET/SDH channelized data carrying many independent unframed/framed T1 or E1 streams.

Connecting the optical SFPs to the fiber optic ports, the 2 ports (Port 3, Port 4) on the unit are available for OC-3/12 STM-1/4 channelized testing.


SonetExpert™ with SFPs Configuration

Physical Specifications

  • 2 - Channelized Ports (STM-1/STM-4)
  • Single Mode or Multi Mode Fiber SFP support with LC connector
  • USB 3.0 Port
Sync Loss, HDB3 Violation, Carrier Loss, Frame Error, Remote, Distant MF, AIS, BPV Errors, CRC Errors, Frame Errors, Transmit Under Run, Receive Over Run
Power and Dimensions:
  • Length: 8.45 in. (214.63 mm)
  • Width: 5.55 in. (140.97 mm)
  • Height: 1.60 in (40.64 mm)
  • +9 volts, 2.0 Amps

The SEC comprises of hardware and software receiving and transmitting data using SONET and SDH networks and communicating with the GL Soft T1/E1 Analyzer application. The GL's Soft T1/E1 Analyzer provides the same functionalities as GL hardware based T1/E1 Analyzers with the difference that T1/E1 frames are multiplexed into SONET/SDH frames and transmitted over optical lines. The SEC architecture creates the appearance of a GL's Soft T1/E1 Analyzer seamlessly operating over SONET/SDH lines similar to a hardware based T1/E1 Analyzer physically connected to multiple T1/E1 lines.

SEC software consists of:

  • SEC service
  • SEC monitor and control
  • SEC configuration utility
  • SEC logging facility

The service requires Administrator authority and is usually launched from the SEC monitor and control application. The service uses SonetExpert™ device to transmit and receive data over optical lines using SONET/SDH protocols. The service demultiplexes T1/E1 frames received from the SONET/SDH and sends them using User Datagram Protocol (UDP) to GL’s Soft T1 E1 Analyzer. It also multiplexes T1 E1 frames into SONET/SDH frames and transmits over optical lines using SonetExpert™ hardware.


Architecture of SonetExpert™ Channelized Analyzer

When SEC Monitor and Control is running, it does not affect the functionality of the SEC service, the application just monitors the service. The latter is running undisturbed regardless SEC Monitor and Control application is up or it is closed. The monitoring features allow users to see the operational status of the service otherwise invisible. Users can open and close SEC Monitoring and Control application as many times as needed without disturbing operations. The only way to cause interference with the service operation is to invoke the “STOP SERVICE” function.

The picture below shows GUI based SonetExpert™ eChannelized Analyzer T1 E1 Service Monitor, which provides users with the following functionality:

  • Starting and stopping the SEC service
  • Configuring the SEC service
  • Launching STEAs
  • Viewing and clearing the SEC service log
  • Displaying alarms, error counters and operational statistics

SEC Monitor and Control Window

SEC Configuration Utility

The utility configures SONET/SDH parameters, UDP endpoints for T1/E1 frame data transfer between STEA and SEC services, T1/E1 channels used and clock setting of SONET/SDH ports.


SEC Configuration Utility

SONET/SDH Data Rates

SONET is the North American standard (termed OC-N) defined in Telcordia GR-253-CORE and ANSI T1.105. STS-1 (Synchronous Transport Signal Level -1) is the basic level of electrically framed signal format in SONET. Higher-level signals are integer multiples of STS-1, creating the family of STS-N signals, for N = 1, 3, 12, 48, 192 & 768.  The optical counterpart for each STS-N signal is designated as OC-N (Optical Carrier level-N).

SDH is the Asian and European standard (termed STM-N) defined in ITU G.707 and G.708 standard. An STM-N (Synchronous Transport Module Level-N) are the frame structures used in the SDH.

The following table details bit rates of SONET and SDH.

North American Standards ITU-T Designation    
Electrical Level Optical Level Data Rate (Mbps) Payload Rate (Mbps) SDH Equivalent T1 Equivalent SonetExpert™






28 T1s






84 T1s







336 T1s







1344 T1s







5376 T1s





















86016 T1s


SDH Signal Mapping

This configuration tells which mapping option should be used when multiplexing the T1/E1 channels from STM-1/OC-3. SONET/STS-3/OC-3 maps to 84 T1 Ports. SDH/STM-1 maps to 63 E1 Ports. On the Rx path, the mapping of the received frames will be detected automatically, this configuration has effect only on the Tx path.

Two mapping schemes are supported for both T1 and E1.

The below diagram depicts various T1/E1 to STM-1/STM-4 signal mapping possibilities in SonetExpert™ Channelized Analyzer hardware.

  • E1_VC3 (Mapping path E1 = STM-4 → STM-1 →AUG-1 → AU-3 → VC-3 → TUG-2 → TU-12→E1)
  • E1_VC4 (Mapping path E1 = STM-4 → STM-1 →AUG-1 → AU-4 → VC-4 → TUG-3 → TUG-2→TU-12→ E1)
  • T1_VC3 (Mapping path T1 = STM-4 → STM-1 → AUG-1 → AU-3 → VC-3 → TUG-2 → TU-11→ T1)
  • T1_VC4 (Mapping path T1 = STM-4 → STM-1 → AUG-1 → AU-4 → VC-4 → TUG-3 → TUG-2→TU-11→ T1)

VC Mapping in GL’s SonetExpert™

SONET Signal Mappings

The below diagram shows various T1/E1 to OC-12 mapping possibilities in SONET. The paths colored in green color are supported on GL’s SonetExpert™ hardware.

The T1 and E1 mappings for OC-12 in SONET are as below:

  • STS-12 --> OC-12 --> STS-3 --> STS-1 --> VT-Group --> VT2 --> E1
  • STS-12 --> OC-12 --> STS-3c --> STS-1 --> VT-Group --> VT2 --> E1
  • STS-12 --> OC-12 --> STS-3 --> STS-1 --> VT-Group --> VT1.5 --> T1
  • STS-12 --> OC-12 --> STS-3c --> STS-1 --> VT-Group --> VT1.5 --> T1

Accompanying Basic Software / Features

Almost all the basic applications and optional applications supported by T1 E1 analyzers are also supported by SonetExpert™ Channelized Analyzer. For example, capturing and transmitting an entire OC-3 / STM-1, and OC-12 / STM-4 signals simultaneously, or performing ISDN, or SS7 analysis, can be performed using the software accompanying the SonetExpert™ Channelized Analyzer.

A list of all the basic applications and other optional applications (requiring additional licenses) are listed here.

Some of the applications currently supported are discussed below -

Application #1: Protocol Analysis

The protocol analysis can be performed on the packets captured non-intrusively by connecting the channelized Rx Ports of SonetExpert™ to a Fiber Optic tap - as shown below. The SonetExpert™ is capable of selectively identifying and forwarding the T1, or E1 signals from OC-3/12  STM-1/4 signal streams to GL’s wide variety of protocol analysis modules such as SS7, ISDN, CAS, and more.

Application #2: Abis Monitoring

SONET Abis Monitoring

Application #3: ATM to SDH in a 3G GSM Network

SONET atm to SDH 3G GSM Network


Item No Item Description
SEUE02 SonetExpert™ Channelized Analyzer (OC-3/STM-1)
SEUT02 SonetExpert™ Channelized Analyzer (OC-12/STM-4)

SonetExpert™ OC-3/STM-1 Basic E1 Software

SonetExpert™ OC-3/STM-1 Basic T1 Software