The difference between SONET and SDH can get a little confusing because so many people struggle with appropriately distinguishing their differences. Both SONET and SDH are sets of standards used to test fiber optic connections and networks. However, these two sets of tests are designed for specific countries and their unique standards.
SONET and SDH’s essential protocol neutrality was designed and developed for the transport of fixed length Asynchronous Transfer Mode (ATM). The data that is transferred during ATM is known as frames or cells.
SONET and SDH testing ensures that cellphone networks, data storage networks, or really any kind of network using optical fiber or ethernet cables run smoothly as cells move between various sources in their network.

What is SONET?


SONET is short for Synchronous Optical NETworking and is a standardized protocol that transfers multiple digital bit streams synchronously over an optical fiber using a laser or light-emitting diodes (LEDs). 
Before the development of SONET, the synchronizing sources of various connected circuits were operating on a slightly different rate and phase to prevent congestion. SONET allowed for the simultaneous transport of multiple varying circuits of different origins within a single framing protocol.
The previously used, complex, internal structure is replaced with large, concentrated frames where ATM cells, IP packets, and ethernet frames are placed. This method allows for a much higher level of efficiency.
The SONET standard was set by Telcordia and the American National Standards Institute (ANSI) and is currently used in the United States and Canada.

What is SDH?

Synchronous Digital Hierarchy (SDH) is the standard used by Europe and most of the world when it comes to testing fiber-optic networks and ethernet connections. While SDH is considered the world standard, because it’s used in every country outside of the US and Canada, it was actually developed after SONET. Essentially SDH performs the same function as SONET, but with a few different metrics. These standards were eventually formalized by the International Telecommunication Union.
When asking yourself which standard you need to set your connections, it will boil down to what country you're located in. However, both testing protocols achieve the same goal using slightly different metrics for their respective tests and many testers offer both standards.

What Testing Equipment is Needed for SONET and SDH Testing?

Application modules are designed to perform testing on ethernet and/or fiber-optic cables and their network. Some of these tools are capable of testing both ethernet and fiber-optic networks. 
For work on major cable networks, fiber-optic capabilities are typically all that’s needed -- especially out in the field. Of course, there may be instances where ethernet connections within a data storage unit or lab may need to be tested as well.
Before you order your testers, check your countries standards, what cable you’re testing, and how much time your tests will take. If you’re unsure, or you need to order your testing equipment before this information is available, several devices can run multiple standard tests on either type of cable. 
Most instruments can perform tests on 10 Gigabyte ethernet. If you need to perform tests on 100g and 1000g ethernet cable, make sure the device you choose is capable of doing so before you buy or rent.


What Instruments are Available for SDH and SONET Testing?

VIAVI Solutions, Anritsu, and EXFO are some of the top suppliers on the market for hand-held devices and testing kits for SDH and SONET testing. Devices like the VIAVI T-BERD 8000 Scalable Multitest Platform tests TDM/PDH and SONET/SDH at OC-3/STM-1 to OC-192/STM-64, respectively. 
The T-BERD 8000s are extremely popular for testing because they can perform a wide variety of tests on both ethernet and fiber-optic cables. With a built-in SATA solid-state hard drive and a Li-Ion battery, you will be able to perform tests in difficult places.
Here are some additional devices to consider: 
  Finding the right device with the correct specifications can be difficult but it’s not impossible. One thing that should not be overlooked, is how long you’re going to need this testing equipment.

Renting SDH and SONET Testing Equipment

Technology is constantly improving and changing. As a result, it can be difficult for businesses to keep up with the proper testing equipment needed to ensure their networks remain functional and competitive.
Many of these testing units can easily cost thousands of dollars or more. If you need to supply a fleet of testers or you only need to perform tests once a year, buying these devices is not your best option economically. 
Fortunately, Advanced Test Equipment can rent a set of the devices you need for a set period, saving you tens of thousands of dollars. Visit our SONET | SDH category page for a full list of our SDH and SONET testing equipment or speak with one of our experts (800)-404-2832.