Praseodymium-Doped Fiber Amplifier (PDFA) offers high gain, high saturation power, and a low noise figure, making it ideal for use within optical networks as either a booster amplifier or preamplifier. The fiber amplifier technology offers an alternative to semiconductor amplifiers (SOAs) with improved optical performance by eliminating the signal distortions typically associated with gain saturation in SOA devices. Each fiber amplifier is enclosed in a compact, turnkey bench top package with FC/APC (2.0 mm narrow key) input and output connectors. The system integrates a pump laser and precision current driver to adjust the pump power in the amplifier. The current adjustment, done through an adjustment knob on the front panel, varies the amplifier gain. The amplifier includes input and output isolators to protect the input laser source from any amplified spontaneous emission or back reflections, as well as to prevent the pump light from exiting the amplifier.
The PDFA gain can be controlled in constant current control (ACC) mode via the front panel interface. The pump current of the amplifier is adjustable through the instrument's front panel, allowing the user to vary the gain and output power. The display screen shows the pump level, as well as the temperature and emission status. An indicator light is also included on the enable button to show when the internal laser is active. In addition to this mode of operation, the PDFA can be operated in constant power control (APC) and constant gain control (AGC) modes using a command-line interface via USB connection with a PC. These modes of operation allow the user to control the amplifier for a fixed output power level or a fixed gain value. The amplifier automatically adjusts the pump current in order to maintain the power or gain target values.
For added safety, there is an interlock connector located on the rear panel that must be shorted in order for the output to be enabled. This can easily be configured to be triggered by doors to disable the fiber amplifier in unsafe conditions. An enable button must be set to activate the amplifier, and a green LED indicator displays the current state of the unit. There is a 3 second delay before the fiber amplifier turns on, and the user is warned by the rapidly blinking LED.
The amplifier includes a universal power supply allowing operation over 100 to 240 VAC without the need for selecting the line voltage. The fuse access is conveniently located on the rear panel.
Adjusting the Fiber Amplifier Gain The default operation mode of the amplifier is by controlling the pump current. This operation mode is referred to as the automatic current control (ACC). The fiber amplifier gain and output power are controlled by varying the pump current set-point. The system specifications represent the performance at max operating set-point (100%). Each unit is shipped with a test data sheet that shows the amplifier output power at two different input power levels (0 dBm and -30 dBm) as a function of the pump current set-point. The data can be used as a reference to adjust the pump current set-point for a desired gain level. In addition to the ACC mode of operation, it is possible to operate the PDFA in automatic power control (APC) and automatic gain control (AGC) modes.
