With the widespread use of WDM systems, more and more problems are beginning to emerge, especially for long distance transmission WDM systems, where signal attenuation has become the primary problem. Although some emerging amplifiers such as EDFA, FRA, SOA have solved the problem of signal attenuation, they are expensive in terms of cost, particularly dangerous in terms of use (FRA) and cannot be used when incompatible equipment needs to be connected (e.g. 1300nm carrier wavelength conversion for optical networks). Since we have different providers for our fibre networks and different standards, we need a certain device to transition from one fibre network to another. This is where the WDM optical amplifier repeater family (OEO) comes into play.

Signal regeneration has not been implemented in OEO earlier. Initially, the OEO was only used to convert the wavelength of an external input signal into a wavelength suitable for a WDM system. This conversion process was also used to stabilise the frequency and amplify the power of these signals, making them compatible with EDFA in DWDM systems. As the medium OEO evolves from 1R to 3R, the complexity of its signal regeneration components increases.                    

The so-called 3R are re-amplification, re-timing and re-shaping.

1R: Re-amplification The 1R does not ‘sort‘ the signal, but simply takes an external input signal and converts it into an analogue signal. This process disregards the integrity of the signal. As a result, if the incoming optical signal is a "rubbish signal", then its analogue version will also be a "rubbish signal". Furthermore, the actual transmission distance of a DWDM system is limited by the fact that the long distance transmission itself may cause signal attenuation.

2R: Reshaping and re-amplification Before the external input signal is re-amplified, it is first sorted out. At this point, the quality of the signal is monitored.

3R: re-amplification, re-timing and re-shaping It is more advanced than the 1R and 2R systems. The signal quality can be monitored more closely and precisely due to the quality data bits embedded inside the signal. These quality data bits inform the system of the health and attenuation of the signal. 3R systems are able to monitor two-way communication.

The WDM optical amplification repeater family (OEO) plays an important role in WDM systems, especially in DWDM systems, where the OEO extends the transmission distance of the network by converting wavelengths (1310 to 1550) and amplifying optical power with balanced amplification, timing extraction and recognition of regenerative (3R) optical signals. OEO with optical conversion (O-E-O) is usually used in conjunction with optical multiplexers in terminal multiplexers. OEO is widely used for long distance transmission on various trunk lines. The advantages of OEO are its small size, economic safety and simple installation, which is why it is used in many optical transmission applications.

Principle of operation

The most important feature of OEO is the ability to receive, amplify and re-transmit signals via different wavelengths without changing the data/signal content. Today, wavelength conversion can only be achieved by means of an OEO, which works as a regenerator, converting the optical input signal into an electrical signal, generating a logical copy of the input signal by means of a new electrical pulse amplitude and waveform, and using this electrical signal to drive the transmitter to produce an optical signal with a new wavelength.

HTF’ OEO card can support many kinds of transmission rate: 400G, 200G, 100G, 40G, 25G, 10G, etc