PDFA vs SOA for Amplifying O-band WDM signal
There are currently two commercially available options in amplifying 100GBASE-LR4 signal – PDFA and SOA. Both have pros and cons, and they are summarized in the following.
In general, PDFA surpasses SOA in optical performance. For example, FiberLabs’ PDFA offers higher maximum output power (+20dBm) and small signal gain (>25dB) than comparable SOA-based amplifiers. In addition, SOA cannot be used as a booster amplifier due to low output power and nonlinear optical effects.
On the other hand, SOA-based amplifier is generally smaller in size and is commonly used as a preamplifier in a 100GBASE-ER4 transceiver.
O-band optical amplifier performance comparison summary
| FiberLabs’ PDFA | SOA | |
| Maximum output power | up to +20 dBm | < +10 dBm |
| Small signal gain | > 25 dB | ∼ 20 dB |
| Noise figure | < 7 dB | < 8 dB |
| Amplifier configuration | Booster/inline/pre-amplifer | pre-amplifier only |
| Footprint | Maximum 4 amplifiers in 19-inch chasis |
Can be integrated inside transceiver module |
FiberLabs’ 19-inch 1U chasis can carry maximum four PDFAs, and a booster amplifier and pre-amplifier can coexist. This allows network operators to install PDFAs at only one side of the LR4 transceiver pair (see below), simplifying the installation and maintenance of reach extension.
Schematic of one network configuration, where using PDFA has an advantage in extending the reach. PDFA is installed at only one side of the network, while SOA needs to be installed at both sides.