EDFA

EDFA stands for Erbium-Doped Fiber Amplifier. The BaySpec’s EDFA series products are mainly for metro applications.

S-, C-, and L-Band: S-Band (short band) is not well defined. Usually it is the spectral window from about 1450 nm to 1530 nm. C-band (conventional band) is the spectral window from about 1525 nm to 1565 nm corresponding to the strong amplifying range of the erbium-doped fiber amplifiers. L-band (long band) is the spectral window from about 1568 nm to 1610 nm.

Wavelength Range (nm) is the spectral region over which the EDFAs are operated and provide effective light amplification for signal channels.

Gain (dB): An optical amplifier is nothing but a laser except that no feedback exists in amplifier configurations. The external pump, either optically or electrically, generates population inversion in amplification media, through which an incident light signal is optically amplified. An important measure for the amplification ability of an optical amplifier is gain. In optical amplifiers, Gain is defined as the ratio of output to input optical power and is usually expressed in dB through

Gain(dB) = 10 × log10[Pout/Pin ]

Gain Saturation: When the optical power is too high, the gain coefficient starts to decrease, thus reducing the power of the signal undergoing amplification. This effect is called gain saturation. More precisely, when the optical power P exceeds the saturation optical power Psat, the gain becomes saturated. Gain saturation is an important characteristic of an EDFA, especially in a booster application and largely determines the maximum output power (saturated output power, see below).

Amplified Spontaneous Emission (ASE) is the amplified optical power resulting from the spontaneous (i.e., not stimulated by any signal photons) release of photons within the gain spectrum of an EDFA operation due to the random decay of erbium ions from the metastable state to the ground state.

Backward ASE Power is the amount of ASE power emitted from the EDFA input port.

Backward Remnant Pump Power is the amount of pump power that is not absorbed by the rare earth ions and is accessible at the input port of the amplifier.

Forward ASE Power is the amount of ASE power emitted from the EDFA output port.

Forward Remnant Pump Power is the amount of pump power that is accessible at the output port of the EDFA.

Saturated Output Power (dBm) is the maximum output power Pout from an optical amplifier when the optical power within the amplification medium reaches the saturation optical power Psat. Note that the saturated output power Pout is usually less than the saturation optical power Psat because the latter is the sum of the input pump power and output power. For EDFAs, the pump wavelengths are 980 nm or 1480 nm and the amplification wavelengths are across 1528-1562 nm.

Small Signal Gain (dB) is the amplifier gain, when operated in the linear region, where it is essentially independent of the input signal power at a specific signal wavelength and operating conditions (e.g., pump power, temperature, …).

Noise Figure (dB) quantifies the noise performance of an optical amplifier and is defined as the signal-to-noise ratios of the input and output signals:

nf = [SNR]in/[SNR]out

It is usually expressed in units of dB, given by

NF = 10 × log10{[SNR]in/[SNR]out}

NF is often referred to as a figure of merit when one is evaluating the noise performance of an optical amplifier.

Polarization Sensitivity (dB): The maximum change in an optical amplifier gain due to changes in the state of polarization (SOP) of the amplifier input signal.

Return Loss (Input or Output) (dB) is the ratio of input optical power Pin to the reflected optical power Pref, in units of dB. It is usually a positive number.

Return Loss = 10 × log10[Pin / Pref]

Pump Wavelength (nm) is the operating wavelength of external pumping lasers. For EDFAs, it is either 980 nm or 1480 nm, or both.

Pump Current (mA) is the current externally supplied to the pumping diode lasers.

Pump Forward Voltage (V) is the voltage produced by the flow of current through the pump laser diode when it is biased for a specified output power.

Operating Current and Operating Voltage (A & V) are electrical parameters applied to pump semiconductor lasers.

Total Power Consumption (W) is the total energy supply in the unit time, including external pumping to the semiconductor lasers and power loss in the thermoelectric coolers.

Operating Temperature (°C) is the temperature range over which the device can be operated and maintain its specifications.

Storage Temperature (°C) is the temperature range over which the device can be stored without damage and can be operated over operating temperature according to its specifications.

Gain Flattening is a process by which an uneven gain profile is adjusted by counteracting the gain spectrum of an erbium-doped fiber amplifier.

Gain Tilt (dB) is the non-flatness of the gain of an EDFA. Gain tilt contributes to the cumulative degradation of an optical signal as it passes through multiple amplification stages. Specifically, the effect is a distortion of the gain spectrum in an erbium-doped fiber amplifier caused by an unexpected change in the power of the input signals entering the amplifier.

Gain Flatness (dB) indicates the degree of the gain variation over its range of operating wavelengths. A flat gain profile is highly desired. This can be achieved by using the gain flattening filters.

Gain Flattening Filter is a static spectral device that flattens the output spectrum of an erbium-doped fiber amplifier.

Dynamic Gain equalizer is a dynamic spectral device that flattens the output spectrum of an erbium-doped fiber amplifier. The output spectrum of an erbium-doped fiber amplifier may change in time so that it requires real-time adjustment of spectrum over various wavelength ranges.