The Evolution And Trends Of Fiber Optic Transceivers

When it comes to fiber optic transceivers, we can easily think of a lot of different package formats like 1X9, GBIC, SFF, SFP, etc.
1X9 package optical module was first produced in 1999, with SC head, is fixed optical module products, usually directly solidified on the circuit board of communication equipment, used as a fixed optical module. Then, 1X9 package optical module was gradually developed towards miniaturization and hot-pluggable.
Fiber optical module products began to develop in two aspects. One is hot-pluggable optical module, which became GBIC. The other is small, with LC head, directly solidified to the circuit board, which became SFF 2X5, or SFF 2X10.
Both GBIC and SFF optical modules have been widely used.
GBIC module, once widely used in switches, routers and other network products. The old Cisco and other vendors’ switched and routers have been widely adopted GBIC modules. Compared with 1X9, GBIC has obvious advantages, hot-pluggable feature makes GBIC can used as an independent module, users can easily maintain, update fiber optic transceivers and fault location. However, with the continuous development of network, GBIC module’s shortcomings also gradually appeared. The main disadvantage is its large size, resulting in a smaller density of service boards, boards can not accommodate a sufficient number of GBIC, unable to adapt to the trend of rapid development of network.
SFF module, is another branch of fiber optic modules’ evolution, now is widely used in EPON system. In the EPON ONU system, all adopt SFF module. The main reason why ONU use SFF optical module is EPON ONU products are usually placed in the users, require fixed rather than hot-pluggabe. With the rapid development of EPON technology, SFF market is gradually expanding.
SFP is the latest fiber optic transceiver, also is the most widely used module currently.
SFP module is hot-pluggabe (like GBIC) and small (like SFF). Using LC head, and its size is small as 1/2 to 1/3 as that of GBIC Module, which greatly increases the port density of network device, adaptable to the trend of the rapid development of the network, so it has been the most widely used. Currently the main equipment manufacturers, without exception, no one abandoned GBIC products and only produce SFP transceiver. Thanks to the centralized standards, SFP modules from different manufacturers can be compatible with each other, SFP is available as a stand-alone network equipment.
According to the rate, fiber optic transceivers can be divided into 100Base, 1000Base (Gigabit) and 10GE for Ethernet, 155M, 622M, 2.5G and 10G for SDH, which all have been widely used, and now the rate of 40G and 100G has appeared. The 10G modules are widely used in the main transmission, mainly include XENPAK, X2, XFP and 10G SFP+.
XENPAK module is an important step in the evolution. XENPAK in architecture for media access controller provides a XAUI interface. Serializer / deserializer to 10 Gbps available payload and forward error correction overhead assigned to the interface 4 channels, each one line signaling rate decreased to 3.125 Gbps. Compared with non-hot-pluggable, XENPAK module is very attractive, but it can not meet the demand of some important market. XENPAK power is typically 10W, caused a certain influence on the structure of size. Because it increases the printed circuit board manufacturing costs and reduce valuable trace space.
X2 transceiver also uses electrical interface(like XENPAK), but there are a few exceptions. X2 provides a 4-bit port address space, a bit less than XENPAK. X2 also reduces the number of power pins, and the bottom plate and electrical grounding utilities. X2 retained the 4 vendor-specific pin as Xenpak. In optical technology, X2 supports 10GbE, OC192 SONET, 10GFC and other standards.
XFP (10 Gb small form factor pluggable module), it provides a architecture with its four-channel interface different from XENPAK. XFP is a single-channel serial module using a XFI (10 Gb Serial Interface) connection at full speed, can replace XENPAK and its derived products. Without serializer / deserializer, XFP is smaller, cheaper and less power consumption.
SFP + module is smaller than XFP, the circuit for clock and data recovery is transferred to the card from the chip. SFP + module compressed size and power consumption through putting the CDR and electronic dispersion compensation outside the module.
No matter how fiber optical module develops, it has its own direction. Currently fiber optical transceiver mainly toward the directions of miniaturization, low cost, low power, high speed, long distance and hot pluggable.