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What is the difference between EML and DML lasers? How to choose?
Knowledge Base + 2024.01.24

Both EML (External Cavity Laser) and DML (Distributed Feedback Laser) lasers play an important role in optical modules for optical communications and other optoelectronic applications.

I. What are EML and DML lasers?

EML lasers, or electro-optic modulated lasers, work based on the photoelectric effect. It modulates the amplitude and phase of the laser by applying a voltage to the semiconductor material, thus realizing high-speed optical modulation.EML lasers have the advantages of high speed, high efficiency, low noise, etc., and have a wide range of applications in fiber optic communications, optical imaging, optical sensing and other fields.

DML lasers, i.e. directly modulated lasers, work on the principle of modulating the amplitude and phase of laser light based on changes in carrier concentration in semiconductor materials. Through the direct modulation of the laser, it can realize the rapid control and regulation of the laser.DML laser has the advantages of low cost, low power consumption, easy to integrate, etc., and has a wide range of applications in the field of fiber optic communications, optical computing, optical sensing and other fields.

Second, how to distinguish and select EML and DML two kinds of lasers

1, understand the factors that determine the type of laser:

The difference between the two types of lasers, EML and DML, lies mainly in their operating mechanisms and spectral ranges.EML lasers usually use an external modulator to generate lasers, and they can work in a larger frequency range and have higher speeds.DML lasers, on the other hand, use a direct modulator to generate lasers, and they usually work at a lower frequency but have higher power.

2. Understand the spectral range of lasers:

DML lasers are lasers that implement feedback through a grating or other structure. It can usually operate in a wider spectral range, such as 1550-1650 nanometers. DML lasers, on the other hand, can usually only operate in a narrower range, such as 1550 nanometers.

3. Understand the operating speed of the laser:

EML lasers can work at higher rates, such as 10 Gbps, because they use an external modulator, while DML lasers usually work at lower rates, such as 1 Gbps, because they use a direct modulator.

4. Understand the application scenarios of the lasers:

EML lasers are used as light sources in DWDM (Dense Wavelength Division Multiplexing) systems to emit stable and narrow spectral lines, enabling them to transmit large data streams for high rate optical communications.The tunability of EML allows flexibility in selecting different wavelengths in optical communication systems, thereby increasing fiber utilization and data transmission efficiency.

DML lasers are typically used for shorter distance optical communication transmissions. Although their output spectra are relatively broad, they are still advantageous in some low-speed data transmission and short-distance communication.

In summary, to distinguish and select between the two types of lasers, EML and DML, factors such as laser type, spectral range, operating rate and power need to be considered. Only with a comprehensive understanding of these factors can the type of laser best suited to the application be selected.

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