FAQ about SOA

Is it possible to manufacture a SOA covering a wide wavelength range from 1.2 to 1.6 µm like an LD?

Theoretically, 1.2 to 1.6-µm emission layers can be fabricated on an InP substrate, but the long-wavelength side is narrower in polarization-independent SOAs.

Is an isolator required in front of a SOA? If yes, why?

An isolator is inserted on the input side of the SOA for preamplifier applications to prevent stray light entering the fiber network system.

What is the difference between BOA and SOA?

SOA is a polarization-independent optical amplifier, while BOA is a polarization-dependent booster optical amplifier that is used mainly as a power amplifier for light sources requiring maximum output power.

How do you achieve low polarization dependence?

Polarization Dependent Gain (PDG) is reduced by applying appropriate tensile strain in the horizontal direction to the SOA active layer.

What level of reflectivity is required for the AR coating on the SOA facet? What are the effects of increased reflectivity and enhanced SOA resonance?

The reflectivity of the AR coating is about 0.2% or less. The ASE spectrum and gain ripple increase as reflectivity rises, leading eventually to oscillation.

How does SOA response time compare to EDFA?

The response time is the gain response time when the SOA is driven by pulsed current. The SOA response speed is very fast compared to EDFA, and a SOA can be used as an optical gate switch with a high extinction ratio of more than 40 dB.

What is the SOA ASE spectrum ripple?

The ASE spectrum ripple is ≤1 dB, and the typical value is about 0.5 dB.

Does Polarization Dependent Gain (PDG) change with the incident angle of the input light to the SOA?

Although PDG may change as the incident angle increases, excessively large changes degrade the optical coupling efficiency with the SOA chip. Therefore, any feasible change to the incident angle does not affect PDG.

Is a bandpass filter used on the output side of the SOA at evaluation of saturation characteristics?

No bandpass filter is used.

Can small-package products be mounted on a QSFP?

Small-package products could be mounted on CFP/CFP2, but it is difficult on QSFP due to space limitations, so we recommend moving to chip-on-carrier products.

Does SOA support 400GE?

Although the benefits of SOA are not significant for short-distance transmissions such as LR4, SOA has been used for long-distance transmissions over 40 km.

Does a multiple input application require a SOA for each wavelength?

Generally, a single SOA amplifies multiple wavelengths collectively, such as the application example in 100GBASE-ER4.

What are the advantages of the SOA+PIN configuration compared to APD?

SOA has a larger gain and is expected to extend transmission distances more than APD.