We all know that DFB lasers are widely used in daily life, so do you know how to use DFB lasers? What should I pay attention to?

The full name of DFB laser is "distributed feedback laser", which is generally referred to as "DFB" in our circle. It is actually a kind of semiconductor laser, but it is much smarter than the ordinary FP laser.

How to use DFB laser

The structure of DFB is similar to that of an ordinary edge-emitting laser, except that it adds a grating structure inside the chip, which is equivalent to "planting" a feedback channel with a fixed wavelength in the chip. In this way, it can only emit a single wavelength laser when it works, and it will not jump around in multiple modes like ordinary FP.

In use, DFB lasers are usually equipped with a constant-current driving power supply and a temperature control system (TEC). These two are the basis for its stable work.

The use process is roughly as follows:

Check pin definition

The pin arrangement of different manufacturers is different, and some also have isolators, thermistors, TEC, etc. Before wiring, you must refer to the original Pin definition, especially the polarity of power supply.

Temperature control

The wavelength of DFB laser will change with temperature, and the wavelength will drift about 0.08nm for every 1℃ increase.

Therefore, it is generally necessary to use Butterfly package with temperature control to stabilize the temperature at the target point, such as 25℃, through TEC and NTC temperature control loop. If you are a communication module, you will also fine-tune the wavelength by controlling the temperature to align it with the optical fiber channel.

Matters needing attention when using DFB laser

Say a few points that are most likely to "step on the pit" in practical engineering.

Electrostatic protection should be in place

DFB chips are particularly sensitive to ESD. Be sure to wear an anti-static bracelet before powering on, and the equipment should be grounded, especially in dry season.

The fiber end face should be clean.

Sometimes the optical power you measure is high and low, but the end face of the optical fiber is dirty. Dust will burn at high power density and even reflect back to the chip.

Pay attention to avoid optical feedback.

What DFB fears most is the feedback light, which will affect the lasing stability. When the reflection is serious, the output wavelength will drift and the power will shake.

Therefore, as long as it is not in a completely isolated closed system, the output must be connected with an isolator (ISO), which is the most basic protection.

The above is about the application of DFB laser and what should be paid attention to. I hope it will help you.