XENPAK is a standardized form factor for 10 Gbps Ethernet fiber optics transponders.
XENPAK optics are used in datacom optical links only (not telecom). The electrical interface to the host board is also standardized and is called XAuI (4 x 3.125 Gbps ).XENPAK optics are the oldest of the 10G form factors. Xenpak optics have the same connector type as an X2 module (SC). Cisco introduced the Xenpak form factor, and Juniper Networks is now producing Xenpak optics as well. There are a limited amount of line cards and switches from Cisco which are using Xenpak optics. The WS-X6704-10GE line card, the most popular line card for the Cisco 6500/7600 series, is still driving the demand of Xenpak optics.
Because Xenpak optics are an older technology and are more bulky than the newer optics modules, they are not really used in the newer product line. Production of Xenpak optics have been replaced by the X2 modules, and this was then replaced by the SFP+.There Xenpak optics convertors which will convert the Xenpak to a SP 0G ? the CVR-XENPAK-SFP10G. Although this is not an official Cisco device, it is offered as part of the Solid Optics product line. The Xenpak adapter has the advantage of letting you use a the increasingly industry-norm SFP+ optic, considered the form factor of the future.
The Xenpak optics come in 4 different versions: SX, LX, EX and ZX. The SX version will work on Multi Mode fiber, the LX, EX and ZX work only on Single Mode fiber. The LX will reach a maximum range of 10km, the EX of 40km and the ZX of 80km. Xenpak optics always have a Tx (sending laser) and a Rx side (receiver). The difference between the sending power (in dB) and the receiving power (in dB) is called the power budget and will determine the distance an optic can cover, where the laser light (in nanometers) also has an important role. Solid Optics offers the complete CWDM and DWDM spectrum for Xenpak optics.