A so-called WDM is a wavelength-selective coupler. The optical frequency multiplexing method, wavelength division multiplexing (WDM), splits the wavelengths in such a way that each spectral colour has its own transmission channel.
Double your transmission capacities with SM WDMs
Single mode WDM are mainly used for telecom applications. If only one fibre is available the transmission capacity can be doubled by using WDM. The components can be terminated with all common connectors. Depending on your application, WDMs are available in fusion technology (FSM) or with thin optical filters (TFF).
One strength of optical data transmission is the ability one has to transmit multiple wavelengths and their corresponding measurement signals simultaneously without interference. In many cases different signals are designated for different receivers and special filters ensure that only the required wavelength reaches the detector. SEDI offers a broad range of WDM filters.
1310 nm / 1550 nm / 1625 nm Singlemode WDM
For instance, the 1310-nm, 1550-nm, and 1625-nm single mode WDMs are offered by ATI. With their help a fibre can be tested during operation. At 1310 nm and 1550 nm they transmit signals without any limitations. At 1625 nm a signal can be sent to test the transmission path.
The single mode 1625-nm blocking in-line filters allow the 1310-nm and 1550-nm communication wavelengths to pass, but do not let the 1625-nm OTDR wavelength through. In this way, the test signal is kept away from the receivers disturbed by the 1625-nm single mode WDMs.
Compact 1310 / 1550 nm WDM
The guidelines for development of the new high isolation WDM from SEDI called for compact sizes and high optical isolation. By integrating the WDM and the filter into one compact housing, a significant amount of space was won compared to SEDI’s standard cascading components.
Insertion loss and directivity are typically 0.5 dB (minimum 55 dB). Isolation is specified by 50 dB at 1310 nm and 20 dB at 1550 nm. The second value can be increased by using an optical inline filter.
In addition to the high isolation values, the broad wavelength range is also noteworthy (1260 – 1360 nm and 1480 – 1625 nm). The device is based on 9/125-µm fibres with a primary jacket of 250 µm and comes inside an invar housing that measures 40 mm in length and 2.9 mm in diameter.