Know About Identifying RX/TX Power Range on SFP Modules


The demand for fiber optics is increasing by the day, and hence it is crucial to understand the ports and network devices used here. This helps select the right devices with the required power and configuration. SFP or small form factor pluggable modules are a transceiver that can be connected to an SFP port on a switch in the network. These modules are designed to connect fiber optic cables in the network. They are similar to RJ45 connector ports used to connect copper cables. These are used for data as well as voice communication applications and offer immediate connectivity. RX and TX stand for receiver and transmitter sensitivity which is an important part of the optical power calculation. This post discusses the ways to identify RX/TX optical power on SFP modules.

RT/RX performance on SFP

What is RX/TX Optical Power Calculation?

Simply put, this calculation is done to find out the difference between RX or receiver and TX or transmitter sensitivity. Optical power is measured in dBm. At times, it is also measured in milliwatts or microwatts. The transmitting power leaving the transmission end device is expected to maintain signal level within the transmission range. The receiving power must be within the receiving power range and is the level of signal received from the transmitting end device. Optical power or power budget indicates the amount of light available for fiber optic connectivity. This is calculated by measuring the difference between transmitting and receiving power (TX-RX). Most switches have a command line interface and display where users can view the transceiver information such as RX power, TX power, supply voltage, and so on. Based on this data or readings, you can determine if the cable is functioning as required. The upper and lower limits for TX and RX are adjusted by manufacturers based on set standards. So, if the TX value has fallen way below the lower limit, mostly below -30 dBm, this indicates that there is no signal being transmitted over the cable.

The transceivers can be single mode as well as multimode. Multimode transceivers are designed for short distance transmission up to around 500 meters, while single mode transceivers are designed for long-distance transmission which may span a few kilometers. When calculating an optical power, the minimum value for transmitter and maximum for receiver is identified so that maximum allowable loss can be calculated.

What Are Optical Power Ranges?

Aside from the RX/TX optical power calculation, there are other factors to be considered for transmission distance, such as cable length, link length, splicing points, fiber signal attenuation, connectivity of components, and so on. A good quality transceiver would always have a high value of optical power budget. Here are optical power ranges which may indicate something specific:
  • An ideal value for transmitter power is -6dBm, but it could range between -1 and -7 dBm. For receiver power, the value could range between -1 and -9 dBm.
  • At times, the actual transmission may not happen, and the transmission power may fall below -25 or even -30 dBm. This may happen due to electromagnetic interference or heightened noise levels at the receiver end.
  • The other scenario may be transmission power falling below -10 or even up to -15dBm. This may imply signal loss, faulty connector or cable, splicing issue.

If you are a business owner looking to upgrade your network or switch to fiber optics, do consider these aspects related to optical power calculation, no of SFP ports on a switch, use of media converters in a blended network vis-à-vis your requirements and budget. Also, ensure you source these devices from a reliable and certified manufacturer and supplier. VERSITRON is a leading manufacturer and supplier of a variety of network devices such as media converters, switches with SFP modules and ports for RJ45 connectors, and other fiber optic devices.

Available SFP Modules (Ordered Separately):

Model
Speed (Mbps)
Wavelength
Media
Distance
Connector
TX Pwr.
RX Pwr.
Temp
RFQ
TSRJ45
10/100/1000
-
Copper
100m
RJ-45
-
-
0 to 70°C
FEMM
100
850nm
MMF
2km
LC
-10 ~ -4
< -24
0 to 70°C
FE2MM
100
1310nm
MMF
2km
LC
-20 ~ -4
< -31
0 to 70°C
FE10SM
100
1310nm
SMF
10km
LC
-15 ~ -8
< -34
0 to 70°C
GBMM
1000
850nm
MMF
62.5µ: 220m
50µ: 550m
LC
-9.5 ~ -4
< -18
0 to 70°C
GB2MM
1000
1310nm
MMF
2km
LC
-9 ~ -1
< -19
0 to 70°C
GB10SM
1000
1310nm
MMF/SMF
MM 62.5µ: 220m
MM 50µ: 550m
SM 9µ: 10km
LC
-9.5 ~ -3
< -20
0 to 70°C
GB20SM
1000
1310nm
SMF
20km
LC
-4 ~ +1
< -24
0 to 70°C
GB40SM
1000
1550nm
SMF
40km
LC
-4 ~ +1
< -24
0 to 70°C
GB70SM
1000
1550nm
SMF
70km
LC
0 ~ +5
< -24
0 to 70°C
GB100SM
1000
1550nm
SMF
100km
LC
0 ~ +5
< -30
0 to 70°C
GB10SFA
1000
Tx: 1310nm
Rx: 1550nm
SMF
10km
LC
-3 ~ -9
< -21
0 to 70°C
GB10SFB
1000
Tx: 1550nm
Rx: 1310nm
SMF
10km
LC
-3 ~ -9
< -21
0 to 70°C
GB20SFA
1000
Tx: 1310nm
Rx: 1550nm
SMF
20km
LC
-3 ~ -8
< -23
0 to 70°C
GB20SFB
1000
Tx: 1550nm
Rx: 1310nm
SMF
20km
LC
-3 ~ -8
< -23
0 to 70°C
GB40SFA
1000
Tx: 1310nm
Rx: 1550nm
SMF
40km
LC
-3 ~ +2
< -23
0 to 70°C
GB40SFB
1000
Tx: 1550nm
Rx: 1310nm
SMF
40km
LC
-3 ~ +2
< -23
0 to 70°C
GB60SFA
1000
Tx: 1310nm
Rx: 1550nm
SMF
60km
LC
0 ~ +5
< -24
0 to 70°C
GB60SFB
1000
Tx: 1550nm
Rx: 1310nm
SMF
60km
LC
-2 ~ +4
< -25
0 to 70°C
GB80SFA
1000
Tx: 1310nm
Rx: 1550nm
SMF
80km
LC
-2 ~ +3
< -26
0 to 70°C
GB80SFB
1000
Tx: 1550nm
Rx: 1310nm
SMF
80km
LC
-2 ~ +3
< -26
0 to 70°C
10GBMM
10G
850nm
MMF
62.5µ: 30m
50µ: 80m
OM3: 300m
LC
-7 ~ -1
< -10
0 to 70°C
10GB10SM
10G
1310nm
SMF
10km
LC
-6 ~ +1
< -14
0 to 70°C
10GB40SM
10G
1550nm
SMF
40km
LC
-1 ~ +2
< -16
0 to 70°C
10GB80SM
10G
1550nm
SMF
80km
LC
0 ~ +4
< -23
0 to 70°C


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