To help you make an informed choice, we have listed key parameters to consider when choosing an optical transceiver:
Data Rate and Form Factor: The multi-source agreement (MSA) defines the different transceiver form factors. Popular form factors include SFP+, SFP28, QSFP+, QSFP28, QSFP56 and so on. Different switching equipment support different data rates and data formats. Always ensure that your transceiver is compatible with your network switch.
Data Format : NRZ is the preferred encoding scheme for 28 Gbps rates. PAM4 has become the standard for medium and long distance data transmission where each link transmits 50 to 56 Gbps per lane.
The image below shows the difference in eye between NRZ and PAM4 modulation.
The image below gives a breakdown of transceiver by data rate, form factor and data format.
Reach and Fiber Type: A singular advantage of fiber over copper is the distance a signal can be transmitted over fiber. The reach also defines the type of fiber to be used, with multi-mode being used for shorter reaches and single mode for long reaches.
Connectors: The most common types of fiber cable connectors used in optical transceivers and networks are LC and MPO/MTP though there are some new types of connectors available now.
LC duplex: This is a connector that everyone is familiar with. LC duplex is widely used in 40G and 100G transceivers.
MPO/MTP Connectors: These can be 8/12/24 fiber and are most commonly used in 40G, 100G and 400G transceivers.
CS Duplex: CS is a new connector type typically used in 200G and 400G transceiver connections. The reduced size allows double the density in patch panels compared to a LC connector.
SN connector: This is designed primarily for OSFP/QSFP-DD and allows four duplex connections in a QSFP-DD/OSFP without using a separate fan-out.
Operating Wavelengths: 850nm, 1310nm and 1550nm are the prime wavelengths used in fiber optics transmission.
850nm : Typically used in short distance multi-mode fiber connections below 500m.
1310nm : Used in Single Mode, generally used for transmission for high data rate transmission.
1550nm : Used in single mode long reach links at data rates below 10Gbps because of its low attenuation. Beyond 10Gbps modulation, 1550nm is hardly used due to its’ unacceptably high fiber dispersion. For higher speed modulations, 1310nm is the wavelength of choice for 40km and 80km links.
Wavelength grids: WDM (Wavelength Division Multiplexing) technology allows for transmission of multiple wavelengths over one fiber using different wavelengths.
CWDM : CWDM (Coarse Wavelength Division Multiplexing) fiber transceivers support wavelengths ranging from 1270nm to 1610nm with a spacing of exactly 20nm. Each channel uses a different color.
DWDM : DWDM (Dense Wavelength Division Multiplexing) can accommodate 40, 80 or even 160 wavelengths with narrower wavelength spans which are as small as 0.8nm, 0.4nm or even 0.2nm.
MWDM: MWDM (Medium Wavelength Division Multiplexing) used in 5G networks is relatively new technology. It is based on the 6 wavelengths of CWDM, shifted by 3.5nm left and right to expand to 12 wavelengths (1267.5, 1274.5, 1287.5, 1294.5, 1307.5, 1314.5, 1327.5, 1334.5, 1347.5, 1354.5, 1367.5, 1374.5nm).
Operating Temperature Range : Standard operating voltage of an optical transceiver is 3.3V. Most applications need only commercial temperature transceivers at 0 to 70 degC. Vitex also offers extended ( -20 to 85degC) and industrial temperature (-40 to 85 degC) transceivers for outdoor and rugged applications.
Cost
- Budget:
- Balance the need for performance, distance, and data rate with your budget constraints.
- While third-party transceivers can be cost-effective, ensure they are fully compatible with your equipment.
Fiber Connector Types
Below are some available transceiver optical port connector types:
The SC fiber connector is somewhat of a predecessor to the LC connector, as the two share the same basic design. The difference between the two is the SC ferrule is roughly double that of the LC. Duplex LC and SC as shown above are fairly straightforward: one side is your Tx, the other side is your Rx. MPO-12 and MPO-16 get a little more complicated. The 12 and the 16 imply the number of fibers contained inside the cable. “12” in MPO-12 indicates 12 fibers, however it is only utilizing 8 lanes. SN is a newer type of fiber connector designed and optimized for 400G applications. It is basically 4x dual LCs compacted into a connector. It enables 4 duplex lanes from a 400G transceiver. The MDC connector is also a newer variety and largely used for 400G.
As far as fiber endface polish types there is UPC (Ultra Physical Contact) or APC (Angle Physical Contact). UPC fiber endfaces are “flat” while APC fiber endfaces are polished at an eight-degree angle. APC gives better optical return loss which gives a slightly better link budget than UPC. However there are situations where UPC, the slightly less expensive choice, may be good enough in terms of optical performance. Whichever polish type is chosen for your application, keep in mind that APC and UPC cannot be mated together.
Temperature Rating
In what type of environment will your transceiver be utilized? Is it going to be in a data center that is temperature controlled, or is it being plugged into a node out in the field in Houston, Texas where it can hit >100ᣞ in the summertime? You should be able to get just about any transceiver type in either industrial temp or commercial temp ratings. Generally the specified temperature ranges for transceivers are as shown below. However these may vary slightly depending on the manufacturer.
- Commercial Temperature Range: 0 °C to 70°C
- Industrial Temperature Range: -40°C to 85°C
- Extended Temperature Range: varies by manufacturer
Before ordering be sure to ask whether your transceiver will go through rigorous environmental testing cycles in an engineering lab, both from a hardware and system level perspective.
Now you know what questions to ask in determining which transceivers to use for your applications. The next question is, who will you have that conversation with?
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