Aerospace Log #4 – Conversion of light signals

The difference between On-Board- and Plug-in-Transceiver

Fiber optic systems are the ideal solution for transmitting large amounts of data, as they are superior to copper-based connections in some respects. These include, but are not limited to:

  • High data rate
  • Good eavesdropping security
  • High transmission range
  • Low weight

However, to enable data exchange between electronic systems using light pulses, these must be processed from an electrical signal and converted back after transmission. Fiber optic transceivers are used here.

What are Fiber Optic Transceivers?

A transceiver is a small optoelectronic component that is available in different sizes and performance dimensions depending on requirements. To fulfill its task - the conversion of electrical signals into light pulses - the transceiver has several components. Depending on the transmission method, the electrical signal can be encoded before being converted into an optical signal. The conversion then takes place using a light source in the transmitter, which feeds the modulated light signal into the optical fiber. Incoming light pulses are detected by the receiver component, decoded and translated into an electrical signal that the transceiver forwards to the connected board.

Basically, optical converters are divided into plug-in and on-board (also known as mid-board) versions. Plug-in transceivers offer a modular solution for optical interfaces that enable rapid adaptation to changing network requirements. They are particularly suitable for the fast connection of optical systems in easily accessible locations, as the fiber optic connection can be established using a simple plug-and-play procedure. They are preferably used in data centers, internal company networks in industry, but also used in telecommunications.

As an alternative, on-board transceivers represent a solution that enables the connection of optical and electronic systems in a smaller installation space and with less weight.

On-board transceivers enable integration in a small installation space.

How to choose the right transceiver

Both types offer different characteristics which must be selected depending on the technical requirements of the application. Some important decision criteria for selecting the right transceiver are:

  • Glass fiber used: As described in the previous Aerospace Log #3, there is a fundamental difference in transmission using single-mode and multimode optical fibers. The type of optical fiber used is decisive for the selection of the appropriate transceiver.
     
  • Required data rate: The maximum transmission rate can limit the overall performance of the system if the transceiver power is too low. High-performance transceivers currently achieve data rates of up to 800G per module. Through parallel channels and aggregation, total transmission rates in the terabit range can be realized in systems.
     
  • Available interface: Optical fibers can be connected via a variety of connectors. LC connectors for serial optical connections (e.g. 10G, 25G, 100G LR4) or MTP/MPO connectors for parallel optics applications (e.g. 40G, 100G, 400G SR4) are common on the market. The transceiver used must allow the fiber to be connected accordingly.

On-board transceivers are particularly suitable for use in embedded systems such as mission computing. The key factor here is the high demands placed on the assemblies. With a lower weight and a smaller form factor, the converters mounted directly on the board fit seamlessly into the systems and enable a more flexible board architecture. They support the transmission of the high data volumes that have to be processed due to a large number of subsystems and deliver reliably high signal quality even under extreme loads.

Plug-in transceiver from ODU

ODU offers two versions for plug-in transceivers:

  • 100G QSFP SR4 CTemp-850nm
  • 400G QSFP-DD SR4 CTemp-850nm

Both models are based on multimode transmission with a wavelength of 850 nm and use VCSEL technology for short ranges of up to approx. 100 meters via OM4 fibers. They enable high-performance and reliable optical data transmission and are particularly suitable for applications that require high bandwidths and robust interfaces.

The combination of advanced Expanded Beam Performance technology with high-quality on-board transceivers forms the optimum transmission system for high data volumes in harsh environments. The direct connection of the optical converters to a robust interface eliminates critical weak points and ensures maximum signal quality even under the most demanding conditions.

Plug-in transceivers enable rapid adaptation to changing network environments.