Characterisation, Measurement & Analysis
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Fibre Optics

  • How to Save Time When Testing Multiple Cable Types

    Changing out reference cables during the insertion loss and return loss testing process to accommodate new DUT types can cause downtime for a manufacturing line and drastically reduce the efficiency of the cable production process.

    With single channel DUTs and reference cables, the issue may seem inconsequential. However, in the modern fibre production line every minute counts; any method that can speed up time per test, minimise the time between tests, and prevent downtime are ways to make your cables more profitable.

    Figure 1: An OP940 insertion and return loss meter with multiple reference cables: MTP, LC Duplex, SC, and FC connectors.

    One way to minimise this downtime is to connect multiple different reference cables to your multi-channel insertion loss and return loss test set in advance.

    Having reference cables that match the different connector types you commonly test or that will be tested that day at that test station will minimise the time it takes to start testing new DUT types.

    Additionally, it allows connector-level insertion loss testing for many types of hybrid cables without a complicated test setup if you have a reference cable that matches each.

    Ideally, the setup includes enough channels to accommodate the different reference cable types at once, as shown in Figure 1. Discuss with your sales engineer your testing needs and they can recommend an ideal test setup and channel count.

    Figure 2: Connector end-faces before (top) and after (bottom) cleaning.

    Finally, having reference cables that are only disconnected from time to time means that you have more repeatable IL/RL results and you can prevent damage to high quality reference cables and the interfaces to the test equipment.

    This will reduce overall downtime and cost associated with troubleshooting and repairing the damage to those connections.

    For further information, application support, demo or quotation requests  please contact us on 01582 764334 or click here to email.

    Lambda Photometrics is a leading UK Distributor of Characterisation, Measurement and Analysis solutions with particular expertise in Electronic/Scientific and Analytical Instrumentation, Laser and Light based products, Optics, Electro-optic Testing, Spectroscopy, Machine Vision, Optical Metrology, Fibre Optics and Microscopy.

  • Measure Latency in Optical Networks with Picosecond Accuracy

    In optical networks where action on a message or signal is time critical, latency becomes a critical design element. Latency in communications networks is comprised of the networking and processing of messages, as well as the transmission delay through the physical fibre. Measuring and optimising this optical transmission delay can be critical in diagnosing latency issues in a data centre or maintaining quality control in the production of precision fibre links. Fortunately, the Luna OBR 4600 can measure this latency with picosecond accuracy.

    Specifically, latency is the time delay of a light signal to travel, or propagate, in an optical transmission medium. The latency is related to the length of an optical fibre by the equation:

    Where L is the length, c is the speed of light in a vacuum and n is the index of refraction for the optical fibre.

    Because the Luna OBR can measure loss and reflections in short fibre networks with ultra-high resolution (sampling resolution of 10 µm) and no dead zones, it is straightforward to extract the exact length or latency of a segment of fibre or waveguide by analysing the time delay between reflection events. In fact, the OBR 4600 is able to measure latency or length this way with an accuracy of <0.0034% of the total length (or latency). For a 30 m optical fibre, for example, this corresponds to an overall length measurement accuracy of better than 1 mm, which is equivalent to a latency measurement accuracy of about 5ps for standard fibre. Note that this is the absolute accuracy; actual measurement resolution will be much higher.

    The example illustrates a typical application of measuring any differences in the length or latency of two fibre segments, each approximately 50 m in length. An OBR 4600 scans both segments and the latency of each segment is indicated by the distance between the two reflections at the beginning and end connectors of the segments. In this example, the difference in latency is found to be 95ps. For this fibre, this is equivalent to a difference of about 19.3 mm in length.

    Measuring length and latency is only one application of the versatile OBR reflectometer. For an overview of the OBR and common applications for ultra high resolution optical reflectometry, download Luna’s OBR white paper below.

    Fibre Optic Test & Measurement with Optical Backscatter Reflectometry (OBR)

    Optical communications technology is rapidly evolving to meet the ever-growing demand for ubiquitous connectivity and higher data rates. As signalling rates increase and modulation schemes become more complex, guaranteeing a high-fidelity optical transmission medium is becoming even more critical.

    Additionally, modern networks are relying more on photonic integrated circuits (PICs) based on silicon photonics or other developing technologies, introducing additional variables into the design and deployment of robust high bandwidth optical systems.

    Measurement and full characterisation of loss along the light path is a fundamental tool in the design and optimisation of these components and fibre optic networks.

    While different types of reflectometers are available to measure return loss, insertion loss, and event location for different types of optical systems, Optical Backscatter Reflectometry (OBR) is a very high resolution, polarisation-diverse implementation of optical reflectometry that dramatically improves sensitivity and resolution.

    See what you’ve been missing with traditional optical instrumentation in this white paper.

    Topics include:

    • Reflectance And Return Loss
    • Measuring Return Loss
    • Optical Backscatter Reflectometry (OBR)
    • Luna OBR Reflectometers

    Click here to download the white paper.

    For more information please email or call 01582 764334.

    Lambda Photometrics is a leading UK Distributor of Characterisation, Measurement and Analysis solutions with particular expertise in Electronic/Scientific and Analytical Instrumentation, Laser and Light based products, Optics, Electro-optic Testing, Spectroscopy, Machine Vision, Optical Metrology, Fibre Optics and Microscopy.

  • Ultra High Resolution OSA: a perfect tool for optical Orthogonal Frequency Division Multiplexing (OFDM) measurement and adjustment

    The Ultra High Resolution OSA (UHR-OSA) proposed by APEX Technologies remains a very important tool not only to measure the optical OFDM (Orthogonal Frequency Division Multiplexing) signal spectrums even with few tens of MHz spacing sub-carriers but also to adjust and adapt it to other modulation techniques.

    APEX-UHR-OSA incessant need in OFDM research area

    APEX UHR-OSAs have found a wide industrial and academic success marked by the incessant demand of researchers and experts in all aspects of the OFDM technique. Indeed, more than 30 APEX-UHR-OSAs are currently used throughout the world by several universities such as Dublin City university (IRELAND) [1], Melbourne university (AUSTRALIA), IT AVEIRO (PORTUGAL), Bangor university[2],… and industries such as Orange Labs [3], KDDI R&D Lab [4],…

    What is OFDM?

    Optical OFDM (Orthogonal frequency division multiplexing) is a promising format for the next generation of long-haul and access networks because of its high spectral efficiency and the resistance to a variety of dispersions including chromatic dispersion (CD). The basic principle of OFDM technique is to carry information using several hundred sub-carriers which transport a fraction of the data rate each. The main feature of OFDM resides in the orthogonality of its sub-carriers obtained by spacing each of them with a multiple of the inverse of symbol duration (of the low bit-rate streams).

    Its main advantage is to avoid the inter-carrier interference and to allow spectral overlapping in order to ensure a high spectral efficiency. The orthogonality is maintained by adding a cyclic prefix to each OFDM symbol in order to eliminate the inter-symbol interference (ISI). In terms of transmission, OFDM has received increased attention thanks to its robustness to ISI, namely chromatic dispersion (CD) and polarisation mode dispersion (PMD), provided by the low sub-carrier data rate without any need for complex equalisation at the receiver side. For this reason, increasing the sub-carrier number is very crucial so that each sub-carrier transports the lowest possible bit-rate stream (equal to the nominal bit-rate divided by the number of sub-carriers). In frequency domain, it corresponds to a few ten of MHz (typical 20 MHz to 50 MHz) sub-carrier spacing. Fibre-optic OFDM systems can be realised either with direct detection optical (DDO) or with coherent optical detection (COD).

    What else makes APEX-UHR-OSA so good?

    Figure 1: Double Side Band (DSB) OFDM spectrum measured by APEX-UHR-OSA taken from [5]

    The key feature of the APEX-UHR-OSA is its capacity to measure the OFDM signal spectrum and to display all the sub-carriers clearly even with a few tens of MHz spacing, this is not possible with a traditional grating based OSA resolution (down to 20 pm/ 2.5 GHz). Based on an interferometric method, APEX Technologies UHR-OSA combines high resolution (up to 5 MHz, 0.04 pm), wavelength accuracy (+/- 3 pm) and high dynamic range. These equipment specifications (in particular the resolution) are good enough to see the details and the separation between adjacent sub-carriers (figure 1).

    Click here for more information

  • Ultra High Resolution OSA for Characterising and interrogating Fibre Bragg Grating Sensors

    The APEX Technologies Ultra High Resolution Optical Spectrum Analyser (OSA) can be used to measure the active/passive optical component insertion loss/gain thanks to the possibility to synchronise the internal Tunable Laser Source and the OSA sweepings. In this context, the APEX OSA remains a perfect tool to measure the Fibre Bragg Grating (FBG) Sensor reflection with 1 MHz of resolution, 63 dB dynamic and 0.3 pm wavelength relative accuracy.

    Introduction to Fiber Optic Sensors

    Optical fibres technology was first realised in the 1960s and has developed to be an integral part of modern telecommunications. Over the last few years, fibre optics and optoelectronics industry have seen tremendous amount of innovation and widespread use leading significantly reduced optical component cost with an improved quality. By taking advantage of these economies of scale, fibre-optic sensors were designed to measure the performance and status of optical networks. In addition to telecommunications applications, optical fibre sensors have moved from experimental research applications in the lab to broad usage and applicability in field applications such as oil and gas services, medical and biomedical engineering, electrical power industry, structural monitoring, defence and aerospace.

    Click here for more information.

  • White Paper: The Importance of Verifying a Reference Reflection for Accurate RL Measurements

    High return loss in a network or data centre is an issue that can cause a number of problems ranging from source stability to increased BER and a lower signal-to-noise ratio. As a result, pass/fail criteria on fibre optic connections has jumped in recent years as advancements in polishing techniques have allowed for fibre optic matings with lower reflections.

  • How to make the Big Sky Ultra more flexible?

    Microsoft Word - FOLA.docFOLA – Fibre Optic Launch Adaptor

    The Fibre Optic Launch Adaptor, or FOLA, is a fibre-coupling option for the Big Sky Ultra Nd:YAG laser. The FOLA has been specially developed for applications in harsh environments and it comprises an O-ring sealed, Nitrogen-purged module with factory aligned and fixed optics.

  • Using the Optical Vector Analyser (OVA) for Component Evaluation in a Production Environment

    LUNA_OVALUNA’s Optical Vector Analyser (OVA) fully analyses the optical properties of fibre optic components, modules, and subsystems, providing comprehensive characterisation based on a complete transfer function measurement. This engineering note details how to use the OVA to characterise components in a production line setting.

  • Time Domain Phase Derivative and Time Domain Wavelength Calculations

    LUNA_OVAIn the following note, the time domain phase derivative and time domain wavelength calculations are detailed.

  • Phase Ripple Measurements with the Optical Vector Analyser (OVA)

    LUNA_OVALUNA’s Optical Vector Analyser (OVA) now has the ability to make phase error measurements. This engineering note discusses the “Phase Ripple Linear” and “Phase Ripple Quadratic” options that are now available with OVA software version 3.8 or later.

  • Calculating chromatic dispersion (CD) for fibre measurements using the LUNA OVA

    LUNA_OVAThis engineering note details the steps taken to accurately compute chromatic dispersion from fibre measurements taken using Luna’s Optical Vector Analyser (OVA).

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