What is the full form of EML?

Introduction

Externally Modulated lasers (EML) are a certain kind of laser used in optical communications that transmits highspeed data across extremely huge distances. It was designed to have high optical power, a small linewidth, and fast modulation speeds.

Due to its capability to transfer data at fast rates over long distances with low signal distortion, EMLs are frequently utilized in optical communication systems, such as fibreoptic networks. EMLs' external modulation is an important component in modern communication systems since it allows for high data speeds by superimposing the data signal onto the laser beam. Also, EMLs can be used in microwave photonics, sensing, and other scientific uses that require highly effective laser sources of information.

Working Principle of Externally Modulated Laser

A ContinuousWave (CW) laser beam is modulated using an external modulator as part of the operation of an Externally Modulated Laser (EML). The modulator, which may change the laser beam's intensity or phase using a highspeed electrical signal, is commonly an electrooptic modulator or a MachZehnder interferometer. The modulated data stream is subsequently transferred by the modified laser beam over an optical cable.

Highspeed data transmission is made possible by external modulation by applying the data signal to the carrier frequency of the laser beam. This method, called intensity modulation, allows the ability to transmit highspeed data throughout long distances without experiencing severe signal distortions. The EML's low linewidth further ensures that the transmitted signal is of good quality and is not dispersed.

Due to the flexibility of the External modulation method' modulation form, a range of modulation techniques, such as Onoff keying (OOK), Amplitude shift keying (ASK), and Phase shift keying (PSK), may be employed. EMLs are appropriate for usage in DWDM systems, which allow the transmission of many signals over a single fiber, because of their high power consumption.

Advantages and Disadvantages of Externally Modulated Laser

Advantages of Externally Modulated Lasers (EML) consist of:

• Highspeed Modulation Because of their highspeed modulation capacity, EMLs are appropriate for use in optical communication systems that need highspeed data transport.

• Low dispersion The narrow linewidth of EMLs ensures that dispersionrelated signal distortion in transmitted transmissions is maintained to a minimum.

• Flexibility EMLs are flexible to a range of communication applications since they offer a number of modulation modes.

• High output power Due to their high power consumption, EMLs are suitable for use in Dense WavelengthDivision Multiplexing (DWDM) systems that call for highpower laser sources.

Disadvantages of EMLs (Externally Modulated Lasers) consist of:

• Complexity EMLs are becoming increasingly complex and costly because they require external modulators.

• Low bandwidth Directly modulated lasers (DMLs), which can transmit data through an increased frequency range, have a higher bandwidth than EMLs, which have a smaller bandwidth.

• Temperature sensitivity EMLs are sensitive to temperature variations, which may have an effect on the way they work.

• Excessive energy consumption EMLs have a high power consumption price in comparison to DMLs, which may additionally prevent their use in lowpower systems.

Applications of Externally Modulated Laser

Compared to other fields, externally modulated lasers (EMLs) are utilized in a number of optical communication systems. EMLs can be used in the following ways:

• Fibreoptic communication Due to its highspeed modulation capabilities, low dispersion, and adaptability, EMLs are often utilized in longhaul and local networks in fibreoptic communication systems.

• Microwave photonics For microwave photonics applications including radiooverfiber systems, sensing, and radar, EMLs provide highpower laser sources with powerful modulation capabilities.

• Coherent communication systems coherent optical transmission and coherent signal detection, rely on highquality, shortlinewidth laser sources provided by EMLs.

• Instruments Highpower laser sources with outstanding modulation capabilities are provided by EMLs in scientific instruments such as spectroscopy, lidar, and laser interferometry.

• Applications in biomedicine EMLs are utilised to offer highquality laser sources with highspeed modulation capabilities in biomedical applications including Optical Coherence Tomography (OCT) and fluorescence microscopy.

• Test and Measurement EMLs provide highspeed, steady laser sources with outstanding modulation capabilities for use in test and measurement applications such as biterrorrate testing and optical power measurement.

Conclusion

In conclusion, it should be noted that Externally Modulated Lasers (EMLs) are essential components of contemporary optical communication systems and other scientific fields. They are useful for a variety of applications, including fibreoptic communication, microwave photonics, coherent communication, instrumentation, biomedical applications, test and measurement, because of their highspeed modulation capabilities, low dispersion, and versatility.

While complexity, limitations on bandwidth, temperature sensitivity, and high power consumption are some of the disadvantages of EMLs, ongoing research and development are addressing these issues and improving their performance. In the future, EMLs are expected to play an increasingly significant role in satisfying the increasing demand for highspeed, reliable, and effective communication systems.

Frequently Asked Questions

Q1. What is the difference between EMLs and DMLs?

Ans: DMLs directly modulate the laser's current, whereas EMLs utilize external modulation.

Q2. What modulation format are EMLs using?

Ans: The modulation formats that EMLs can use are OOK, ASK, and PSK.

Q3. What type of output power do EMLs typically have?

Ans: EMLs are capable of producing highpower outputs, which are generally in the few watt to a few mill watt range.