The development of optical transceivers and their future

Nowadays, when we look at the product- and funcionalityrange of optical transceivers , we owe it to a long technical development.

Since the beginning, all transceiver specifications are defined under non-proprietary standards of the Multisource Agreement (MSA) of the SFF Committee. This allows intercomptability of products from different manufacturers.
At the beginning of the development of optical modules, only modules that had to be soldered into the hardware existed. These transceivers came in the 1x9 SFF format and were first used in 1999.

The maintenance of these modules was extremely time-consuming, a better solution was needed.

From now on, the development of optical modules split into two areas. In fixed and removable (hot-pluggable) optics.

In 2000, the first interchangeable module has been developed : The GBIC (gigabit interface converter) transceiver. It has a duplex SC connector and can be used at distances of up to 160KM.
This technological development offered many obvious advantages: In addition to simplifying maintenance, a network for the "pay as you grow" principle has now been established. By pluggable modules the user was easily able to subsequently increase the bandwidth on a network. The introduction of the GBIC modules by many large network manufacturers started the large spreading of this transceiver.

Unfortunately the GBIC module still had one major drawback: The size. The port density and thus the overall network performance declined significantly. Furthermore, for operators of large networks, such as Telecommunications providers, it was not necessary to upgrade the ports later on. In 2001, the actual fixed optics have appeared on the market: 2x5 SFF and 2x10 SFF. These transceivers are substantially smaller than the GBIC. This was now possible by the newly introduced LC duplex connectors and the resulting smaller PCBs (Printed Circuit Boards ) are possible and among other things. SFF optics are currently also still widespread very far. Today they are used, besides the building wiring, in most EPON ONU hardware and have been obtained strongly in importance by the proliferation of EPON networks again.
But in LAN and MAN networks only replaceable modules are used since the introduction of GBICs.

In the year 2002, the form factor SFP (Small form-factor pluggable) was put on the market. This contained a lot of advantages over the GBIC. It has an LC Duplex connector so that the entire design of the transceiver has been reduced to about a half of the GBIC module. This also accounted for the resulting disadvantages of dwindling port density and overall performance. All network manufacturers use SFP modules for entry-level devices or floor distributors till now on.

With the increasing demand for bandwidth an important step in the development of optical data transmission was made. In the year 2005, the first XENPAK modules were developed. These transceivers provide transmission rates up to 10 Gigabits. The Transmission works with an XAUI interface over 4 channels á 3.125 Gigabit. Thereby the bandwidth of the networks could be increased significantly. Ultimately the disadvantages of the technique predominated. High production costs, a too great design, which again led to lower port density, and the relatively high power consumption of up to 10W per port, could not cover the needs of the customers.

As the successor, in the year 2006, the X2 transceiver was published. Like the XENPAK transceiver, the X2 module has an electrical interface. The differences were minimal, but the next decisive step should not be long in coming.

In the year 2007  the first XFP transceiver was published. This offered significant advantages in the 10 Gigabit networking. The transmission is no more realized with four, but only through one serial channel. By that the PCBs could be significantly reduced, so the LC duplex connector could also be used with the XFP. These modules are only slightly larger than an SFP module, which finally brought an increase in port density 10 Gigabit networks. Furthermore, the power consumption, similar to an SFP, is only up to 3.5W.

The final stage of development in the 10 Gigabit transmission form is the SFP+ transceiver. This offers other minor improvements over XFP modules. The power consumption and the size could be further reduced. SFP+ is now the standard form factor for 10 Gigabit networks with all major network equipment.

In 2011, the first QSFP modules came on the market. This allowed a transmission of 40 Gigabit with a hot-pluggable module for the first time. The speed is achieved by four internal 10 Gigabit CWDM channels. The modules are slightly larger than a XFP transceiver and have a tab in the length of the module to be able to remove it from the hardware. QSFP transceivers also have a MPO/MTP connector.

Today there are two variants of these modules. The QSFP-SR , with a range of up to 150 meters on OM4 fibers, as well as the QSFP-LR, with a range of up to 10KM over OS2 fibers. The standards for QSFP-ER , with a range of 40KM, already exist. The BlueOptics will launch this QSFP -ER transceiver in the fourth quarter of 2014 as one of the first manufacturers worldwide.