Last updated on 03/8/2023
The Short-wavelength band (S-band) is one of the optical communication bands, that covers the wavelength range of 1460 to 1530 nm.
Figure 1: Wavelength range of S-band in optical communication.
The S-band has been traditionally used for Passive-Optical Network (PON). Both G-PON (ITU-T G.984.5 Gigabit PON) and E-PON (IEEE 802.3 Ethernet PON) use 1490 nm for downstream data transmission.
The S-band can be used for WDM transmission to increase transmission capacity by increasing the number of channels.
CWDM transmission is generally a point-to-point unrepeatered (i.e. no optical amplifiers) system. S-band optical transceivers are widely available in various form factors (SFP, XFP, SFP+, SFP28) bit rates (1G, 10G, and 25G), allowing maximum transmission distance up to 120 km.
The use of S-band for long-haul repeatered (i.e with optical amplifier) DWDM transmission, in addition to the C-band and L-band, is technically feasible. This is because the S-band meets the following three requirements.
A schematic of DWDM system, in which the S-band is used in addition to the C- and L-band, is shown in Figure 2. Signals from N transmitters are multiplexed by wavelength multiplexer and are launched to the fiber. When amplification is needed, the signals are de-multiplexed to the S-, C-, and L-bands and amplified by three amplifiers; typically TDFA for the S-band and EDFAs for the C- and L-bands. After amplification, these three bands are multiplexed again and launched to the next fiber section. At the receiver, signals are de-multiplexed to individual channels and detected.
Figure 2: Schematic of DWDM transmission system using the S-band.
Such transmission scheme is referred to as “S+C+L-band WDM transmission”, and much attention has been paid on this scheme at R&D level . It is promising technology for upgrading existing optical fiber network as it does not require new fiber cable deployment.
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