How much optical power does a gigabit single-mode module have

Typical Gigabit single-mode SFP modules operate with a transmitter power of -9 to -3 dBm and a receiver sensitivity of around -20 dBm, depending on the specific standard and link distance.Overview of Single-Mode Gigabit SFP ModulesGigabit SFP modules for single-mode fiber (SMF) are designed for long-distance optical links, typically using a 1310 nm wavelength for standard 1000BASE-LX and 1000BASE-EX modules, and sometimes 1550 nm for extended reach modules like 1000BASE-ZX . These modules convert electrical signals from switches or routers into optical signals for transmission over single-mode fiber and vice versa, supporting data rates up to 1.25 Gbps .Transmission Power (Tx)The transmitter power of single-mode Gigabit SFP modules varies by standard and distance:1000BASE-LX (10 km): Typical Tx power ranges from -9 dBm to -3 dBm .1000BASE-EX (40 km): Tx power is usually higher, around 0 dBm to +5 dBm, to compensate for longer fiber attenuation .1000BASE-ZX (70 km): Tx power can reach +4 dBm to +8 dBm, depending on fiber quality and link budget . These values ensure sufficient optical signal strength to reach the receiver while avoiding overdriving the photodiode.Reception Power (Rx)The receiver sensitivity defines the minimum optical power required for reliable data reception:1000BASE-LX: Typical Rx sensitivity is around -20 dBm.1000BASE-EX: Rx sensitivity is approximately -18 dBm.1000BASE-ZX: Rx sensitivity is generally -14 dBm . The receiver must operate within its specified power range to maintain a low bit error rate (BER) and stable 1 Gbps communication.Link Budget ConsiderationsThe link budget is the difference between Tx power and Rx sensitivity, accounting for fiber attenuation, splices, and connectors. For example, a 1000BASE-LX module with -3 dBm Tx and -20 dBm Rx sensitivity provides a 17 dB link budget, sufficient for a 10 km single-mode fiber link with typical 0.35 dB/km attenuation . Extended reach modules like 1000BASE-EX and ZX require higher Tx power and more sensitive receivers to achieve longer distances.Summary TableStandardWavelengthTx Power (dBm)Rx Sensitivity (dBm)Max Distance1000BASE-LX1310 nm-9 to -3-2010 km1000BASE-EX1310 nm0 to +5-1840 km1000BASE-ZX1550 nm+4 to +8-1470 kmThese values are typical for commercial single-mode Gigabit SFP modules and may vary slightly depending on the manufacturer and specific module model . Proper selection ensures reliable optical links and compliance with IEEE 802.3 Gigabit Ethernet standards.