Before starting to talk about the transceivers, we talk about some experiences in our daily life. Nowadays, mobile phones fast become necessary fixtures in our everyday lives and the market of mobile phone hardware and software also booms along with them. When you get a new mobile phone, the first thing you will do is to install all kinds APPs for your phone. But the premise is that you need to have an enough memory to support this. If you have a shopping experience of buying memory card for your mobile phone, you may find that it is very difficult to make a decision. Because there are all kinds of memory cards in the market. When the shopkeeper are very enthusiastic to promote their products: SD card, TF card, CF card or memory stick; 8 G, 16 G, 32 G, 64 G or even 128 G; Class 4, Class 6 or Class 10 etc., your heart just does whisper what the hell they are.
Just as the memory card could be divided into SD card, TF card and memory stick, transceivers have different types and interfaces as well, which is named as “Package Form”. Package Form is the primary basis of transceiver classification and products partition.
As we know, “transceiver” is a compound word that is consist of “transmitter” and “receiver”. Actually, before transceivers have been launched to the market, there have been two devices, transmitter and receiver for use. At that time, the transmitters and receivers were produced and sold by some major telecommunication equipment manufacturer without size standardization, just as those phone chargers had different connectors and lacked interoperability. It’s so inconvenient for users to deploy such kind of transmitters and receivers. Then the manufacturers discussed this issue and defined a game rule named MSA (Multi Source Agreement) to standardize the game. After this, many transceiver-making companies have come into prominence.
The emergence of Gigabit Ethernet (1000Mbps or 1Gbps) brings the data transmission to a new step. RJ45 connectors and network cables have been unable to meet the requirement for long-distance transmission as it can only transmit within 100 meters. Even to Cat6 cable, due to its bandwidth limitation, it is only available for short-distance transmission in fairly good electromagnetic environment. In this case, a kind of optical-to-electrical interface converter is desired, which uses light for interconnection and communication. GBIC, short for Gigabit Interface Converter, can meet this requirement and becomes the first package interface standardized transceiver. The appearance of GBIC is the milestone for the development of transceivers and has epoch-making significance.
As technology continues to improve, the size of transceiver modules has become smaller and smaller. Therefore, mini GBIC, also called Small Form-Factor Pluggable (SFP) module, came to the market. Just as micro SD is upgraded from the SD card, SFP is an upgraded version of GBIC transceiver. It is a compact, hot-pluggable transceiver used for both telecommunication and data communications applications.
In addition to the size, the rate of SFP also becomes faster and faster, such as 1.25 G, 2.5 G, 4 G, etc. However, when came up to 10G, people found that the encapsulation is too small to keep many components. In order to solve this problem, XFP modules were launched as a new transceiver standard.
In Roman numbers, “V” stands for 5 and “X” stands for “10”. So XFP is the 10 Gigabit Small Form-Factor Pluggable modules that can transmit signals at the rate of 10Gbps. Meanwhile, thanks to the advancing technology, the issue that SFP cannot hold so many components in its body to reach 10 G (in 2006) was solved in 2009. Because after three years of development, the components can be designed with high integration and smaller size. This 10G SFP was called SFP+, namely, enhanced small form-factor pluggable. Compared with SFP, SFP+ is in common with it in terms of size, function, definition of connector and so on. For the purposes of classification, the one that can support the rate of 8 Gbps or even higher is called SFP+.
In fact, XFP is not the first 10G Transceiver in the market. The 10G transceiver market has gone through 300Pin and XENPAK/XPAK/X2 before XFP came out. As these types of products are intergrated with SerDes chips, we usually call them transponders instead of transceivers.
There is a growing number of signals transmitted in an electrical interface, so the number of pins in electric connector are increased to satisfy this demand. 300 pins connector is a 30-columns x 10-rows (as shown in the following picture ) and meets the requirement at that time.
In 2002, as a result of technical limitations, people have to try something new to reverse the situation. On one hand, it was difficult to transmit signals through one cable at 10 Gbps on user’s host board. The transceivers engaged the task, challenged the difficulties by putting two electrical SerDes chips—multiplexer chip and demultiplexer chip in the design. In this case, the data rate of user’s host board decreased because 10Gbps series signal is divided into 16 series signals that each series signal is at 644Mbps. On the other hand, at that time, the components in the transceiver are so large that they can not be put in the Small Form-Factor Pluggable module (as the following picture shown).
But as time went by, the capacity of the user’s host boards is improved constantly, resulting that transmitting the signals at the rate of 3Gbps came true. Thus, 16 series signals were changed to 4 series signals so that the size of the transceivers can be smaller. These types of transceivers are called the 2nd generation 10G Transceiver. The first letter of them is “X” (“X” stands for 10 in roman numbers as the above mentioned), such as XENPAK, XPA and X2, which can reach the rate up to 10Gbps.
By 2006, with the pre-emphasis circuit and the equilibrium technology matured, it is no longer difficult to transmit signals at the rate of 10Gbps on a single fiber on the host board. In consequence, the SerDes chip has been no longer needed since then. Additionally, the smaller optical components and higher IC integration have made the miniaturization become possible. 3rd generation transceivers, namely XFP and SFP+, emerged in the market and still in wide use in today’s 10G application.
Developed Trend & Destiny of Transceiver Package Form
As the saying goes, to want fish on the hook, the first thing you should know is what fish likes. When it comes to transceiver, it’s the same situation. The developed trend of transceiver depends on what customers need. And the fact is that customers always need faster, smaller, lower power consumption, more functional, and more cost-effective transceivers. Different package of transceivers have come to the market one wave after another. With the fact that the new generation of transceiver package form will gradually replace the older generation, the old version also need to upgrade otherwise it has to be replaced gradually till disappear. For example, when XFP came to us, the transponder was replaced gradually. By adding tunable technique, the 10G transponders have still been in the market so far. But now SFP+ also achieves tunable technique which indicates that XFP will vanish sooner or later.
“Once, people consider me as the best device to help them achieve signal transmission. Now the new transceiver appears, people starts to fed up with me.” This may be the soliloquy of each transponder’s or older version transceiver’s heart.
In fact, what happens to transponders or older version transceivers is also true of people. If you stop improving yourself you will be replaced sooner or later. People will only hear the new smile, but nobody will care you crying in the corner.
This article is to mark Transponders as well as those older version transceivers which once have gone through a splendid time but finally replaced. Here, I want to end up my post with a Tang poem “Royal Pavilion”:
(General Idea: As time goes by, palace maids get old, while the red flowers in the cold and cheerless palace are still in bloom. Those lonely ladies can only sit there and talk about past glory.)
Wait, wait, is that all? Absolutely not. Actually, SFP+ has not the last laugh after all. New guy called “Parallel” has emerged in the market and a new revolution has began. For more information, please keep an eye on our next week’s blog update.