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Fiber Optics

  • DTS - Distributed Temperature Sensing
  • DAS - Distributed Acoustic Sensing
  • OTDR - Optical Time Domain Reflectometry

Optical fibers are increasingly used in a diverse range of applications. Their ability to transmit information at light speed over long distances and with low loss has made them the primary medium for large volume long range data communication. As such, fiber optic networks can be found in telecommunications systems where they are used for transmitting and receiving purposes. They are also used to deliver a variety of digital services such as internet, HDTV, and video on-demand.

In industrial zones optical fiber can be employed for imaging in hard to reach areas. In addition, being largely immune to electromagnetic or radio frequency interference (EMI and RFI) they offer significant advantages over conventional wiring in environments that may be subject to high levels of radiation.

In recent years techniques have also been developed that allow optical fiber to be used as sensory devices to make temperature, pressure and other measurements. For example, temperature can be determined by activating various sensing materials such as phosphors, semiconductors or liquid crystals with fiber optic links. Their unique capabilities allow fiber optics to be deployed in medicine for imaging and illuminating (such as photoacoustic microscopy and endoscopy), mining (bore hole logging and safe data sharing), automotive (in-vehicle signal and data transmission) and oceanography (hydrophones for seismic waves and SONAR).

The characteristics of light transmission in optical fiber can be affected by physical parameters, such as temperature, strain or pressure. As a result, fibers can be used as linear sensors to locate external physical effects. The process is commonly called distributed temperature sensing (DTS). In DTS light scattering (known as Raman scattering) and wavelength shifting (Stokes Line) are both studied to reveal information about the physical parameters of interest.

A similar process for characterizing optical fiber systems is optical time domain reflectometry (OTDR). The method works by injecting a series of optical pulses into a fiber under test and then collecting light that’s reflected (as either Rayleigh backscatter or Fresnel reflections) from points along the fiber. See figure 1 as an example. In this setup the digitizer acquires the analogue signals coming from the detector that’s receiving the reflected light. The acquired data can then be analysed so that the optical fiber can be characterized. Two key parameters for OTDR systems are their range and resolution. To increase resolution the optical pulses need to be narrow while the sensor and measuring electronics has to be fast enough to resolve each separate event.

With their high sampling rates and resolution Spectrum digitizers are extremely useful devices for acquiring signals from a variety of optical fiber sensing systems. With models offering sampling rates from 5 MS/s to 5 GS/s users can select a unit that best matches their specific application. For example, the fastest sampling rate products can be used to acquire and analyze optical pulses with widths down to the sub-nanosecond range. Spectrum digitizers also offer vertical resolutions up to 16-bit. These models are ideal for applications where increased sensitivity and low-level signal amplitudes may be encountered.


  • Learn on wikipdia about Distributed Temperature Sensing by clicking here
  • Learn on Wikipedia about Distributed Acousting Sensing by clicking here

Spectrum Product Features

  • Sampling rates from 5 MS/s to 10 GS/s
  • Very high SNR and SFDR
  • Resolution up to 16 bits
  • Fast data acquisition including segmented and FIFO streaming modes
  • Signal processing (hardware and software averaging) with SCAPP GPU support
  • On-Board Block Average

Matching Card Families

A/D family
Sample rate
6.40 GS/s - 10 GS/s
12 Bit
A/D family
Sample rate
1.25 GS/s - 5 GS/s
8 Bit
A/D family
Sample rate
130 MS/s - 400 MS/s
14 Bit 16 Bit
D/A family
Sample rate
625 MS/s - 1.25 GS/s
16 Bit

Research Papers

Optoacoustic Image Reconstruction

The University of Bern’s Institute of Applied Physics in Switzerland is testing and developing algorithms used for image reconstruction in optoacoustic imaging applications. Test signals are acquired using an M4i.4420-x8, 250 MS/s, 16 bit, digitizer and a research paper discussing their findings can be downloaded from here:

Research Paper

Optoacoustic Microscopy for Dermatologic and Micro-angiography

At Switzerland’s Institute of Pharmacology and Toxicology and Faculty of Medicine, at the University Zurich, they are using a burst-mode laser triggering scheme and an M4i.4420-x8, 250 MS/s, 16 bit, digitizer to perform rapid acquisition functional optoacoustic micro-angiography. A paper discussing the developed system, and how it greatly enhances the performance and usability of optoacoustic microscopy for dermatologic and micro-angiographic studies, can be found here:

Research Paper

Handheld Photoacoustic Microscopy

The MOE Key Laboratory of Laser Life Science and Institute of Laser Life Science, at the South China Normal University, in China has developed a Photoacoustic Imaging (PAI) pen that can be handheld (performing forward detection and lateral detection) to extend the application of photoacoustic (PA) microscopy to areas such as the oral cavity, throat, cervix, and abdominal viscera. The experimental setup uses an M4i.4450-x8 500 MS/s, 14 bit, digitizer to acquire the sensor signals. A paper discussing the PAI pen and the test results can be found here:

Research Paper

Large Area all-optical Ultrasound Imaging

The University College London has developed a method for large area all-optical ultrasound imaging using robotic control that involves the use of an M4i.4420-x8 250 MS/s, 16-bit digitizer. A white paper on the development can be found here:

Research Paper

Photoacoustic Imaging

Find out how Nanyang Technological University, Singapore, uses a high speed 16 bit Spectrum digitizer M4i.4420-x8 for Photoacoustic Imaging by clicking here:

Research Paper

Ultrasonic 3D Endoscopic Imaging System

See how the Department of Medical Physics and Biomedical Engineering, at University College London, UK, use an M4i.4420-x8 high-resolution digitizer in a miniature all optical ultrasonic 3D endoscopic imaging system by clicking here:

Research Paper

Brillouin Optical Time-domain Reflectometer

At the Changsha University of Science & Technology in China they have used a Spectrum M4i.2210-x8, 1.25 GS/s, Digitizer to acquire high speed pulses in a Brillouin Optical Time-domain Reflectometer (BOTDR) using Discrete Fourier Transforms (DFT). A paper discussing experimental results that show improved spatial resolution and accurate location of distributed sensing is available here:

Research Paper

Analysis of Diode Laser Modulation Wavelengths

The State Key Laboratory of Laser Interaction with Matter, Northwest Institute of Nuclear Technology, China, is using a 1.25 GS/s M4i.2212-x8 Digitizer together with a customized long fiber ring etalon to make measurements and analysis of diode laser modulation wavelengths at high accuracy and response rates. An article discussing their process can be found here:

Research Paper

Optical Resolution Photoacoustic Microscopy

The School of Biomedical Engineering, Tohoku University, Japan is using a 5 GS/s M4i.2230-x8 Digitizer to achieve optical resolution photoacoustic microscopy with sub-micron lateral resolution for visualization of cells and their structures. Details and results of their experimental setup can be found here:

Research Paper

Ultrafast Spectroscopy

At the Technical University of Dortmund, Germany, they are using a 5 GS/s M4i.2234-x8 Digitizer in nonstationary quantum state tomography, adapting the technique to the special requirements of ultrafast spectroscopy. A white paper on the topic can be found here:

White Paper

Secure Key Generation and Distribution

Cryptographic keys are a vital part of any security system as they control everything from data encryption and decryption to user authentication. The Fiber-Optic research Center, at Fudan University in China, has developed a secure key generation and distribution scheme based on the phase noise of an amplified spontaneous emission source. Experimental results, at a bit generation rate of 3.06 Gb/s over a length of 20 km standard single-mode optical fiber route, showed the bit error rate stays under 0.02%. The experimental setup uses an M4i.2221-x8 2.5 Gs/s. 8-bit Digitizer and a paper discussing the research can be found here:

Research Paper

3D Photoacoustic Imaging

The School of Engineering Medicine, Beihang University, Beijing, China have developed a technique for compressed single-shot 3D photoacoustic imaging with a single-element transducer. They setup uses an M2p.5961-x4 125 MS/s, 16-bit Digitizer to collect the transducer signals as outlined in the reference paper below

Reference Paper

Narrowing the linewidth of a DFB Laser Diode

A method for narrowing the linewidth of a DFB laser diode has been proposed and experimentally demonstrated by the Key Laboratory of Optoelectronic Technology & Systems, at Chongqing University, in China. The system uses an M4i.2212-x8 1.25 GS/s, 8-bit Digitizer for fast signal acquisition and a reference paper discussing the development can be found below.

Reference Paper

Optical Time Domain Reflectometer (OTDR) System for Metal Tip Discharge

The State Key Laboratory of Power Transmission Equipment Technology at Chongqing University in China is developing an integrated distributed fiber optic sensor installation method for gas insulated metal enclosed transmission lines, as well as a distributed partial discharge acoustic detection and localization system. Signal collection using and M4i.2221-x8 2.5 GS/s. 8-bit Digitizer, in a coherent optical time domain reflectometer (OTDR) system for metal tip discharge, achieved sensing distances up to 120 m. A research paper discussing the development can be found below.

Reference Paper

Distributed Dynamic Absolute Strain Sensing Technique

The State Key Laboratory of Coal Mine Disaster Dynamics and Control at Chongqing University in China has demonstrated a high-performance distributed dynamic absolute strain sensing technique that synthesizes both phase and Brilloin optical time-domian reflectometry (φ-OTDR and BOTDR). The system uses an M4i.2221-x8 2.5 GS/s,8-bit Digitizer to acquire the signals produced by a balanced photodetector. A white paper discussing the setup and development can be found below.

White Paper

Photoacoustic Imaging (PAI) for Biomedical Applications

At the School of Biomedical Engineering, Tohoku University, in Japan they are researching photoacoustic imaging (PAI) for biomedical applications. The team has created a testbed setup that can accurately measure photoacoustic signals within an intracellular aqueous environment, avoiding risks of the contamination and degradation of the acoustic transducer. Using and M4i.2230-x8 5 GS/s, 8-bit digitizer for acquiring photoacoustic signals coming from an ultrasound transducer in an optical-resolution photoacoustic microscopy (OR-PAM) system. A white paper on the setup can be found below.

White Paper

Testing Fibre-Optic Ulstrasound Sensor

The University College London, in the United Kingdom, has fabricated a fibre-optic ultrasound sensor that does not contain an optically or mechanically resonant sensing element, but instead comprises a simple deformable and reflective structure at its tip, suitable for use in biomedical imaging, metrology and non-destructive testing applications. To test sensor performance an M4i.4420-x8 250 MS/s, 16-bit, Digitizer was used to collect signals from a fibre-optic Fabry-Pérot 126 detector. The sensor performance and test results are discussed in a paper below.

Research Paper

OpUS system combining concurrent Optical Ultrasound and CT Imaging

The University College London, in the United Kingdom, has created a system that allows concurrent Optical Ultrasound and CT Imaging. Using a new free-hand optical ultrasound (OpUS) imaging system the paper linked below discusses the methodology and results. An M4i.4420-x8 250 MS/s, 16-bit digitizer was used to acquire the optical ultrasound signals.

Research Paper

Miniatur Needle Ultrasound Sensot for Optoacoustic Microscopy

At the University of Zurich in Switzerland they have developed a highly sensitive miniature needle ultrasound sensor for optoacoustic microscopy. The optoacoustic signals were acquired using an M4i.4420-x8 250 MS/s, 16-bit Digitizer and the results are discussed in a research paper below.

Research Papers

Photoacoustic Opthalmoscopy and OCT Images

The Nanyang Technological University in Singapore has combined visible light photoacoustic ophthalmoscopy and near-infrared-II optical coherence tomography to make multimodal imaging of the mouse eye. An M4i.4420-x8 250 MS/s, 16-bit Digitizer is used to acquire data for photoacoustic imaging with the results discussed in a white papers below.

Research Papers

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