Owing to its ubiquity, simplicity and low cost, Ethernet, one technology enabling Internet communications, is everywhere, from carrier networks to local area networks, from desktop PCs to the largest supercomputers. And with its widespread deployment, there occurs countless equipment accordingly designed for Gigabit communications, such as SFP+ transceiver. Are you familiar with SFP+? How much do you know about its testing challenges? This text will discuss its key features firstly, and then delve into SFP+ optical transceiver testing challenges.
SFP+ Optical Transceiver Background
As an enhanced version of the small form-factor pluggable (SFP), the enhanced SFP (SFP+) is a hot-pluggable, small-footprint, and multi-rate optical transceiver accessible for up to 16 Gbit/s data communications and storage-area network (SAN) applications. And this SFP+ enjoys the following advantages.
Smaller, Cheaper, More Efficient
Just as the last paragraph mentioned above, the SFP+ module is a variant of the SFP optical transceiver. It simplifies the functionality of the 10G optical module significantly by moving functions, such as clock and data recovery (CDR), electronic dispersion compensation (EDC), 10G SERDES, and signal conditioning. Thus, the SFP+ module requires fewer components, consumes less power, and allows for increased port density. Certainly, it’s also smaller and less expensive compared with the 10-Gigabit small form-factor pluggable module (XFP) form factor.
As SFP+ becomes more prevalent, it’s imperative for engineers to become familiar with some of the key challenges linked to testing SFP+ capable devices.
SFP+ Optical Transceiver Testing Challenges
On one hand, SFP+ gives a hand in reducing the overall system cost. On the other, its physical layer (PHY) and performance are put with new burdens. The SERDES framer interface (SFI) between the host board and the SFP+ module displays great design and testing challenges.
- One challenge attributes to the increased port density and the testing time required for 48 or more ports per rack. For instance, there are 15 measurements each for the host transmitter tests, and each of these measurements using manual methods can easily take from three to five minutes. This means it will take engineers more than an hour per port to complete the required tests.
- The second one that engineers need to consider is: if a measurement fails, how can they determine which component is causing such a failure, and how they debug the issue to arrive at the root cause. Such determinations are especially challenging because of the tight physical packaging and compact designs.
- Another challenge falls on the connectivity. That is: how to get the signal out from the device under test (DUT) to an oscilloscope. Test fixtures are typically required, but questions arise around consequently: whether the fixtures have been tested and validated against the specification.
- The additional problem lies in the fact that the SFP+ specification requires some measurements to be performed using a PRBS31 signal. At a sampling rate of 50 Gsamples/s, the designer can acquire around 40 million unit intervals (UIs). At a sampling rate of 100 Gsamples/s, the instrument can acquire 20 million UIs. However, a PRBS31 pattern has more than 2 billion UIs. Hence, acquiring an entire pattern poses a challenge.
SFP+ transceiver with its compact size has become a popular industry format supported by many network component vendors. And with the above-mentioned points in mind, designers have gained an overview of SFP+ optical transceiver testing challenges. FS is an outstanding and professional SFP+ manufacturer and supplier, available with a sea of high-performance and -quality SFP+ transceivers. Besides SFP+transceiver, FS also supplies QSFP+ transceiver, fully compatible with major brands. For more information about transceivers, you can visit FS.com.