Reliable Fiber Lasers for Distributed Acoustic Sensing

Install and forget!

If you deliver Distributed Acoustic Sensing (DAS) systems for pipeline monitoring, perimeter security, or border control (to name a few), then it is likely that your systems will be installed in harsh environments in remote places.

Wouldn’t it be nice if you could install the system and forget all about it? With our robust and reliable Koheras fiber lasers, you can.

Designed for real-life

We understand that the laser is a key component in your interrogator. It dictates the sensitivity, range, reliability, and failure rate.

Our Koheras lasers are designed for real life. We have combined the all-fiber distributed feedback design with field-proven components from the telecom industry to give you a robust, reliable, maintenance-free, and service-free laser. They’re as low-maintenance as a cactus!

When we say reliable, we mean a typical lifetime of more than 10 years and a return rate of less than 1%.

Over the past 25 years, our customers have deployed more than 20,000 Koheras lasers in the harshest environments. We have lasers on oil rigs, submarines, wind turbines, and even in space.

You do not have to worry about laser supply. We can deliver all the lasers you need when you need them. Every year, our customers deploy more than a thousand Koheras lasers across the planet.

Long-range and high accuracy

To obtain long measurement ranges, our customers typically look for lasers with a long coherence length and low noise to get a high dynamic range. With a Koheras laser, it is possible to obtain measurement ranges of up to 100 km which makes it easier for you to handle your system and lets you save money on equipment.

Ultra-low phase noise (or frequency noise) is a key laser parameter for the sensitivity and accuracy of the sensing system. The high sensitivity of the Koheras laser ensures an excellent detection of acoustic signals.

Due to their intrinsic low-noise design, you get sub-picometer stability and mode-hop-free performance. Do you want to mount them upside-down? No problem. The all-fiber design keeps the laser stable. Install them in the desert? No problem. Temperature changes do not affect stability. Take them for a ride? No problem. Vibration and noise do not distort the signals.

Pick the right laser

If you need a flexible system with more wavelengths, our Koheras lasers are a bit like Lego (although less colorful). You can combine lasers to get the system that best suits you. Use the Koheras ACOUSTIK rack integration to combine up to 16 Koheras BASIK fiber lasers and two matching BOOSTIK line card amplifiers. The ACOUSTIK provides power and control to all modules and you can add and change channels as needed.

References

Here are some publications where others describe their work within DAS, using our Koheras lasers.

• Integrating High-Capacity Self-Homodyne Transmission and High-Sensitivity Dual-Pulse ϕ-OTDR with an EO Comb over a 7-Core Fiber by Xu Liu, Chenbo Zhang, Yi Zou, Zhangyuan Chen, Weiwei Hu, Xiangge He, and Xiaopeng Xie published in MDPI Journals, Photonics , Volume 13, Issue 3, 2026.
• Frequency-modulated continuous wave-enabled single-ended forward sensing over all-passive fiber links for integrated sensing and communications by Yi Zou, Chenbo Zhang, Jiachuan Yang, Zhangyuan Chen, and Xiaopeng Xie published in Photonics Research,Vol. 14, Issue 4, 2026
• Strategies for mitigating polarization fading in a DAS with homodyne detection and delayed self-mixing by Almaz Demise, Fabrizio Di Pasquale, and Yonas Muanenda, published in Journal of Physics: Photonics, Volume 7, Number 4, 2025.
• Near-Field Multisource Localization and Signal Enhancement With ASP-Assisted DAS by Junfeng Chen, Hao Li, Ke Ai, Shuolong Zhu, Cunzheng Fan, Zhijun Yan, and Qizhen Sun published in IEEE Transactions on Instrumentation and Instruments, Vol. 74, 2025.
• Simultaneous Distributed Acoustic and Temperature Sensing System Using a Single Mode Fiber by V P Anand, Neethu Sasikumar, V R Ranjith, and Balaji Srinivasan published in 2024 Asia Communications and Photonics Conference (ACP) and International Conference on Information Photonics and Optical Communications (IPOC), 2024.
• Low-Phase-Noise Frequency-Agile Hybrid Integrated Laser Offering Highly Linear Tuning for FMCW LiDAR by H. Peng, Y. Chen, I. Robles Lopez, G. Lihachev, H. Tian, A. Voloshin, J. Riemensberger, P. Maier, S. Skacel, M. Lauermann, A. Attanasio, S. Randel, W. Freude, S. Bhave, T. J. Kippenberg, and C. Koos published in CLEO 2024, Technical Digest Series (Optica Publishing Group, 2024), paper SM2M.1, 2024.
• Partial Discharge Measurement for Power Cable Using Crosstalk-Free FDM-DAS by Pengfei Wang, Hongjuan Zhang, Pengwei Guo, Yu Wang, Xin Liu, Yan Gao, and Baoquan Jin published in IEEE Transactions on Instrumentation and Instruments, Vol. 73, 2024.
• Integrated sensing and communication in an optical fibre by Haijun He, Lin Jiang, Yan Pan, Anlin Yi, Xihua Zou, Wei Pan, Alan E. Willner, Xinyu Fan, Zuyuan He & Lianshan Yan, published in Light: Science & Applications, vol. 12, article 25, 2023.
• Indoor optical fiber eavesdropping approach and its avoidance by Haiqing Hao, Zhongwang Pang, Guan Wang, Bo Wang published in Optics Express, Vol. 30, issue 20, 2022.
• Non-Invasive Acoustic Monitoring of Gas Turbine Units by Fiber Optic Sensors by Konstantin V. Stepanov, Andrey A. Zhirnov, Stanislav G. Sazonkin, Alexey B. Pnev, Alexander N. Bobrov, and Dmitriy A. Yagodnikov, published in Sensors, 2022.
• Demodulation Scheme with Low Harmonic Distortion for PMDI-TDM Based Fiber-Optic Sensor Array by Jianxiang Zhang, Kun Cheng, Wenzhu Huang, Wentao Zhang, Fang Li published at the 27th International Conference on Optical Fiber Sensors, Technical Digest Series, Optica Publishing Group, 2022.
• The sparsity of the response of a quasi-distributed fiber optic sensing system allows ‘overclocking’ its interrogation by Nadav Arbel, MayaYanko, Avishay Eyal, published in Optical Fiber Technology, Volume 61, January 2021, 102373, 2021.
• Time-expanded phase-sensitive optical time-domain reflectometry by Miguel Soriano-Amat, Hugo F. Martins, Vicente Durán, Luis Costa, Sonia Martin-Lopez, Miguel Gonzalez-Herraez, María R. Fernández-Ruiz published in Light: Science & Applications, 2021.
• On the phase fading effect in the dual-pulse heterodyne demodulated distributed acoustic sensing system by Xiangge He, Xiaohu Xu, Min Zhang, Shangran Xie, Fie Liu, Lijuan Gu, published in Optics Express, Vol. 28, No. 22, 26 October 2020, Optics Express 33433, 2020.
• Performance Improvement of Dual-Pulse Heterodyne Distributed Acoustic Sensor for Sound Detection by Xiangge He, Min Zhang, Lijuan Gu, Shangran Xie, Fei Liu, Hailong Lu, published at Sensors (Basel). 2020 Feb; 20(4): 999. 2020.
• Combined frequency and phase domain time-gated reflectometry based on a fiber with reflection points for absolute measurements by V.A. Yatseeva, A.M. Zotovb, O.V. Butova, published in Physics, 2020.
• Cost-effective solution for phase-OTDR distributed acoustic/vibration sensing by V. V. Spirin, C. A. López-Mercado, J. Jason, J. L. Bueno-Escobedo, P. Mégret, M. Wuilpart, D. A. Korobko, I. O. Zolotovskii, S. G. Sokolovskii, A. A. Fotiadi, published in SPIE LASE proceedings 10903, 2019.

And don’t miss the short article on how thousands of our low-noise Koheras lasers keep a large-scale data network secure, with SFO Technologies.

Don’t know what DAS is?

Distributed Acoustic Sensing is a sensing system based on light. The system consists of an interrogator and some optical fibers. The optical fibers replace traditional discrete sensors and let you measure sound along with its entire length.

The interrogator has a laser inside which sends light pulses into the optical fibers. Most of the light travels forward but some of it is reflected back to the interrogator.

Sound and movements from the environment affect the light. The interrogator analyses the reflected light to figure out what is going on and if it should send an alert. The ultra-precise detection reveals the exact position of the incident, eliminates uncertainties, and saves time.

Distributed Acoustic Sensing (DAS) turns subsea fiber-optic cables into long, continuous sensor arrays that can detect vibration and acoustic activity over many kilometers. By sending coherent laser pulses into the fiber and analyzing the backscattered light, DAS enables real-time monitoring of subsea infrastructure and the surrounding environment. Laser stability, narrow linewidth, and low phase noise are key factors that determine sensitivity, range, and long-term measurement reliability.

Subsea sensing for offshore infrastructure monitoring

Subsea infrastructure is the backbone of offshore energy and communications, but monitoring it has always been challenging due to distance, access, and cost.

Subsea sensing refers to the measurement of physical conditions and events in the water, on the seabed, or beneath it. It helps operators understand what is happening around subsea assets (for example, pipelines, wells, and subsea power/telecom cables), as well as environmental and geophysical activity such as currents, sediment movement, and seismicity.

With DAS, subsea sensing often means using an optical fiber as a long, continuous sensor that provides coverage over many kilometers, rather than relying on a limited number of discrete sensor locations.

How Distributed Acoustic Sensing works

Distributed Acoustic Sensing (DAS) turns a standard fiber-optic cable into a dense array of “virtual sensors.” An interrogator sends short, coherent laser pulses into the fiber and measures the tiny fraction of light that is naturally backscattered from microscopic variations in the glass.

Dynamic strain and vibration along the cable slightly change the optical phase of that backscattered light. Because the return signal is time-resolved, the system can map these phase changes to specific positions along the fiber, producing a distributed measurement of vibration and acoustic activity versus distance and time. The spatial resolution and range are determined by the interrogation scheme and system design.

Why DAS is important for subsea monitoring

Subsea systems are long, remote, and expensive to equip with conventional point sensors, so the main advantage of DAS is continuous coverage. In many cases, the sensing fiber is already part of the installed infrastructure, reducing the need for additional subsea sensor hardware.

With a single fiber route, operators can monitor large areas in real time. This enables early detection of abnormal events such as third-party interference near a cable route, impacts, signs of anchor dragging, or changes in vibration behavior. DAS is also valuable for geophysical and environmental monitoring when the fiber is well coupled to the seabed.

Laser choice is more than just wavelength

DAS interrogators typically use a single-frequency, narrow-linewidth, low-noise fiber laser, often in the 1550 nm telecom window. The wavelength is chosen largely because fiber attenuation is low and components are readily available. However, performance is driven by more than wavelength.

The laser’s coherence and phase/frequency noise directly influence sensitivity, achievable range, and susceptibility to measurement artifacts in phase-sensitive detection. In practical terms, stability, narrow linewidth, and coherence help the interrogator resolve smaller signals over longer distances, while sufficient optical power supports strong signal levels from the backscattered light.

What makes Koheras MIKRO different in this application

In DAS, the laser is not just a light source – it defines the quality of the phase measurement.

A highly stable, low-noise single-frequency laser, such as the Koheras MIKRO E15, helps lower the system noise floor and improves the ability to resolve small signals. This is especially important when pushing for longer reach, finer resolution, or operation in noisy real-world subsea environments.

A mode-hop-free, ultra-stable source also improves repeatability and reduces drift-related interruptions, which is critical for “always-on” monitoring deployments.

From a system integration perspective, an OEM-ready laser module with built-in control and monitoring can simplify design and support robust operation in deployed DAS interrogators. This is particularly true compared to solutions that are harder to stabilize in day-to-day operation.

Design DAS as a system

DAS performance is a system-level outcome: it depends on cable type, installation method, coupling to the seabed, interrogation approach, and signal processing and classification – not just the laser.

That said, for phase-sensitive sensing, the laser remains one of the key enabling components that determines how far and how accurately a DAS system can “listen” along a subsea fiber, and how reliably it can do so over long durations.

For best results, specify and optimize the laser together with the fiber, interrogator, and analytics as one end-to-end sensing chain.

It is also worth noting that fiber-optic sensing is not limited to acoustics – distributed temperature and strain modalities (DTS/DSS) can complement DAS in a subsea monitoring strategy. Contact us to learn how laser choice impacts DAS performance – and how the right source can unlock longer reach and higher sensitivity in subsea sensing.

Contact us to learn how laser choice impacts DAS performance – and how the right source can unlock longer reach and higher sensitivity in subsea sensing.

Read more about DAS and lasers for DAS.

Read more about DAS for Smart Cities.

Why use DAS for smart cities?

Today’s CCTV and discrete sensors give an incomplete picture of what is going on in the city. A DAS system gives you access to a lot of information otherwise unavailable to you.

DAS systems use optical fibers as sensors and let you measure sound along their entire length. It works over long distances and large areas, without any disruption, and sends responses back in real-time.

You can use the existing grid of fiber optic communication networks that are already laid out across countries and oceans. The long stretches of fiber provide you with thorough and continuous data.

DAS systems can be used for a wide range of monitoring applications in the smart city, such as:

• Traffic patterns and density
• Road conditions
• Vehicle type
• Vehicle acceleration, speed, and direction
• Infrastructure monitoring to prevent deterioration of bridges, roads, and tunnels
• Assisting the development of autonomous driving
• Crime detection

Why is Koheras the ideal laser for DAS?

Our Koheras lasers are an excellent choice for DAS systems. To get the highest detection range, you need the lowest possible phase noise – which you get from the Koheras lasers.

They are industrial-grade OEM lasers with a rugged design, a stable performance unaffected by different environmental conditions, and wide temperature ranges in the field.

World-leading acoustic sensing systems use our Koheras lasers due to the intrinsic low phase-noise, the narrow linewidth, and the long coherence length that enable measurement ranges in the range of 100 km.

The most reliable low-noise laser on the market

We have more than 20,000 Koheras lasers deployed in the harshest environments on – and off – the planet. We have lasers on oil-rigs, submarines, wind turbines, and even in space.

With over 25 years of experience, we know they last.

What are the advantages of using DAS?

Distributed Acoustic Sensing, DAS, is a sensing system based on light. The system listens in on everything that is going on in the city. Intelligent software translates the sounds to information and alerts that let you manage traffic and prevent damage to infrastructure.

Optical fibers are perfect sensors

When you use optical fiber as sensors for smart city applications, you get a long list of advantages:

• Fibers are already installed throughout most cities
• Fibers enable measurements of thousands of locations, continuously
• Fibers can cover a large geographical range
• Fibers are immune to electromagnetic interference
• Fibers do not need or carry any electrical power
• Fibers are highly reliable and cost-efficient

Ultra-precise detection eliminates uncertainties and saves time

DAS systems are based on interferometric sensing. An ultra-stable, low-noise laser – such as our Koheras lasers – is built into an interrogator that sends light into the fiber and detects the backscattered light.

Complex algorithms analyze what is going on along the fiber, with high precision.

The interpretation software detects every incident but ensures that only relevant information is passed on to the operators.

Ultra-precise detection reveals the exact position of the incident, eliminates uncertainties, and saves time.

Do you need a laser for your DAS system?

Use DAS systems to monitor all kinds of critical assets and infrastructures, such as power plants, airports, oil-rigs, borders, conveyor belts, pipelines large facilities, etc.

When you point a laser beam at a moving surface, the reflected light is backscattered at a slightly different frequency. This frequency shift is compared to a reference laser beam, allowing you to tell the velocity and displacement of the moving surface.

Koheras lasers are ideal for interferometric sensing

When making interferometric sensing systems – such as laser Doppler vibrometers – it is important to use a laser with a very narrow linewidth to get accurate feedback. With their intrinsic low phase noise and narrow linewidth, the Koheras lasers are ideal for interferometric sensing systems with high demands to dynamic range and sensitivity.

Our unique fiber laser design ensures high wavelength stability and no need for periodic adjustments to the laser’s center wavelength. Furthermore, its true single-mode & mode-hop free operation enables stable system performance.

With documented low failure rates, we proudly deliver the most reliable low-noise lasers on the market. Our lasers boast a long life in demanding industrial environments where uptime is critical due to their inherently compact and robust design.

Useful in many industries

Due to the versatility, the laser Doppler vibrometry method is used to measure a wide range of displacements, from slow to very high-frequency movements.

Precise measurements of mechanical displacement are vital for quality control and structural optimization in the automotive, civil engineering, and aerospace industries.

High optical performance combined with industrial robustness

Our Koheras BASIK MIKRO E15 laser is a popular choice with manufacturers of commercial laser-based vibrometer systems, whether it is single-point, multi-point, or scanning vibrometry. With its robust and compact OEM footprint and very narrow linewidth and low-frequency noise, it combines the best of the scientific and industrial worlds.

Use the Koheras lasers to get:

• Precise measurements of complex and sensitive mechanical structures
• Stable system performance due to true single-mode & mode-hop free laser operation
• Robust fiber laser design suitable for industrial field applications

Publications

• Chun-Hsiung Wang, Hsin Lee, Yu-Hsiang Hsu, Shu-Sheng Lee, Jiun-Woei Huang, Wen-Jong Wu, and Chih-Kung Lee: Photonic Doppler velocimetry for high-speed fragment generator measurements, published in Optics Express, 2020.

Locate oil with Koheras lasers

Optical sensing systems are gaining ground because they offer several advantages over traditional technologies based on electrical transducers, e.g. piezoelectric hydrophones.

New interferometric systems with fiber optical sensors enable longer sensing ranges with high dynamic range and sensitivity. The fibers are passive (no electronics), compact, lightweight, reliable, and can be multiplexed to interrogate extensive sensor arrays. This is key to obtaining a higher return on investment and – ultimately – a lower cost of ownership.

Today only about 30% of an oil well is exploited over time. However, with permanent reservoir monitoring, it is possible to increase the extraction rate and benefit from the existing infrastructure around an oil reservoir.

The optical sensor system listens to an “acoustic signature” from the seafloor, providing means to identify and locate oil “pockets” that are otherwise difficult to access.

Our market-leading low phase noise is crucial for obtaining a high dynamic range and sensitivity in an optical sensor system.

Robust, reliable, and a long lifetime

Our industrial Koheras fiber laser modules have been used in the oil & gas industry for many years and are currently the backbone of several seismic sensor systems.

The fiber laser design is inherently compact and robust. It is developed for a long lifetime in demanding environments where uptime is critical. With documented low failure rates, we proudly deliver the most reliable low noise lasers on the market.

We have more than 15,000 Koheras lasers deployed in the harshest environments on – and off – the planet. We have lasers on oil-rigs, submarines, wind turbines, and even in space. With 20 years of experience, we know they last.

Features

• Low phase-noise provides high dynamic range and sensitivity
• Unsurpassed reliability, suitable for long term operation in harsh environments
• Designed for OEM integration
• Maintenance-free 24/7 operation