Testing Transceivers to Ensure Perfect Interoperability

Transceivers have a specific set of standards that they are supposed to adhere to, in order to ensure perfect interoperability. The concept behind this is critical to how these devices operate and has to be explained in detail, because of how critical they are to the telecom infrastructure. Transceivers have a host interface, usually made from copper and a client interface, which is optical. The host interface is designed so that the transceiver can be used in sync with any device that is compatible with the form factor, while the optical interface is designed so that it provides for communication with other transceivers which implement the optical standards. This makes it possible for the data to be transmitted from one device to another.

SFF, IEEE, OIF and ITU are among the bodies that have worked together to develop a single ecosystem of optical, electrical and management specifications and standards. This makes a multisource environment possible. Open standards and multi-sourcing are considered critical to the working of pluggable transceivers. The aim here is to develop networking equipments that are compatible with transceivers designed by different vendors, so that the devices comply with the set standards and specifications used across different platforms.

This collaboration between the top bodies has made it possible for the telecommunication industry to bring expenses down, to scale up the available resources, reuse devices on various platforms and safeguard the investment made on various optical equipments. Standards such as TP1 and TP4 are considered to be critical to this. They ensure that the devices can be interoperated along with any host transceiver design. Standards such as TP2 and TP3 are the optical standards that define the module’s interface, which ensure interoperability across different devices.

Transceivers should be able to transfer data easily to and from the host card. They should be able to exchange information at the optical level as well with the various management interfaces such as MDIO and I2C. They should also have a fully compatible monitoring system and alarms. To ensure this, one requires a meticulous testing methodology. This is all the more important as electrical interfaces become more sophisticated now than ever in the past. So the integration tests are more important than before, as are the device parameters.

Design Validation and Development Testing Standards

A number of tests are done on the transceiver during the process of design validation and development. In this article, we look at the different test methods employed, with a focus on the critical parameters used.

TP1 – At TP1, the host platform sends the data in the electrical format to the transceiver. The tests done here include rise and fall time, jitter, mask and signal amplitude. The transceiver has to function even when the signals received are very poor.

TP2- TP2 is the point where one verifies whether the device can send through a signal that is fully compliant with the latest optical standards. The tests are done on the transmit power, extinction ratio and wavelength. Jitter, signal rise and falls and mask are also tested. The transmitter dispersion penalty is one of the important parameters that is tested.

TP3 – At TP3, the tests are done to check whether the device works within a specific bit error ratio and within a particular range of power. It has to work within an upper bound called overload and within the lower bound known as sensitivity. The device is tested to see if it detects the worst possible signal. It is also seen whether the electrical signal delivered to the host is within the standard voltage levels, jitter, mask, rise and fall times, and whether it can then be reconverted into the original information when the signal gets through to the data processor.

These are the standard tests run on any transceiver. But the process does not end here. The next step is to program the transceiver EEPROM to make sure that it works well enough on different platforms. Many OEMs want specific information to be programmed; otherwise they raise alerts or fail to enable the ports.

Now, this information can vary from one networking company to another, which is why you need to have a strict control of this process. All the work done on the design and testing of the device is considered wasted otherwise. This means even if you have a transmitter of the best possible quality, it is useless to you if the host card software does not recognise it.

That’s why you should choose 1000 GIG transceivers and other products. Not only are 1000 GIG devices made according to strict standards and undergo a range of design and manufacturing tests, we make sure that they are tested on real platforms just before shipping them off to you. This way you are guaranteed that there is no incompatibility between our products and the various branded host platforms that you are using currently. Our devices work with multiple platforms from different vendors and are essentially platform agnostic. They are consistent and do not display any unpredictable behaviour once installed.

1000 GIG tests make sure of the following…

• The devices are programmed according to the specification.

• There is no question of alarms raised by different host platforms.

• Any faulty conditions are quickly detected.

• The DOM data as reported by the transceivers are in sync with the actual power levels.

• There is a high level of accuracy as per the target specification.

• The transceiver is capable of working even in the worst conditions, passes the line rate and is free from traffic errors.

Research and Development Test Instrumentation

1000 GIG has been investing heavily in research and development and in building world class test instrumentation facilities at its labs. The testing facilities at 1000 GIG stress the sensitivity of the transceivers much beyond the standard specification. The bit error rate is independently verified. Care is taken to see that all inventory and performance data are documented and the trends are closely analysed, so as to look for any potential mistakes or deviations from the normal. This ensures that you get the right kind of quality across different product lines.  The optical connectors of the device are also tested, to ensure that the devices shipped by 1000 GIG are ready to be used out of the box and deliver a high level of performance, to the satisfaction of all customers.