Examine Multicore Optical Fiber for Submarine Cables in Detail

Measurement Technology for Coherent OTDR Examine Multicore Optical Fiber for Submarine Cables in Detail

2025-10-01 From Hendrik Härter | Translated by AI 2 min Reading Time

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Inter-core crosstalk is a problem with multicore fibers, including in submarine cables. The interference can significantly affect data transmission. Measurement technology can help ensure the quality of communication.

Multicore optical fibers transmit large amounts of data. However, interference can significantly affect data transmission.(Image: freely licensed / Pixabay) — Multicore optical fibers transmit large amounts of data. However, interference can significantly affect data transmission.
(Image: freely licensed / Pixabay)

The development of remote monitoring systems for high-performance multicore optical fibers aligns with the increasing data demands driven by developments such as AI and IoT. With their rapid proliferation, global data traffic is expected to continue growing significantly. This necessitates even greater capacity in optical submarine cables that support international communication. Traditionally, optical submarine cable systems use single-mode fibers, which contain a single optical path (core) per fiber.

However, since the possibilities for increasing capacity using a single core are spatially limited, interest in multicore fibers has grown. These integrate multiple independent cores into a single optical fiber cable, thus enabling a significant increase in transmission capacity per fiber.

The Numbers Behind It

The global market for multicore fibers is growing at a compound annual growth rate (CAGR) of around 24% and is expected to reach a market volume of $7.5 billion by 2032. This growth is primarily driven by cloud computing, artificial intelligence, IoT, and high-speed communications such as 5G and 6G. Data centers, new telecommunications infrastructures, and edge computing are considered key drivers of the increasing demand for multicore fiber solutions. Multicore fibers offer significantly increased bandwidth and lower latency compared to single-core technologies, enabling them to meet the growing demand for fast and efficient data transmission on global routes.

The Problem of Inter-Core Crosstalk

Studies on multicore fibers for submarine cables: With the C-OTDR, optical fiber networks can be monitored and faults diagnosed.(Image: Anritsu) — Studies on multicore fibers for submarine cables: With the C-OTDR, optical fiber networks can be monitored and faults diagnosed.
(Image: Anritsu)

A key technology for monitoring and fault diagnosis in modern fiber optic networks is Coherent-OTDR technology (Coherent Optical Time Domain Reflectometry). This measurement method is based on sending laser pulses through the optical fiber. A portion of the light is scattered by microscopic imperfections in the glass and returned to the OTDR as a so-called Rayleigh backscatter signal. The distinctive feature of Coherent-OTDR is that it evaluates not only the intensity but also the phase of the backscattered optical waves interferometrically. This enables a more precise analysis and monitoring of the optical path characteristics.

Analyze Light And Measure Optical Path Properties

Detect interference caused by crosstalk with measurement technology.(Image: Anritsu) — Detect interference caused by crosstalk with measurement technology.
(Image: Anritsu)

As part of the developments by the consortium consisting of KDDI Research, Anritsu, Tohoku University, Sumitomo Electric, Furukawa Electric, NEC, and Optoquest, the feasibility of measuring the optical path characteristics of multicore fibers using Coherent OTDR, as with single-mode fibers, was investigated. KDDI Research designed a new transmission system and built a simulated environment using its expertise. The Coherent OTDR Type MW90010B, developed by Anritsu, was used to analyze the light transmitted through the multicore fibers and measure the optical path characteristics.

For the first time worldwide, it was confirmed that Coherent OTDR can detect faults and be used to measure the fiber loss profile in optical submarine cable systems with multicore fibers. Additionally, the distribution of inter-core crosstalk along the fiber was visualized, including passages through repeaters. This marks a successful step toward the practical applicability of Coherent OTDR in multicore fibers and will accelerate the adoption of this technology in optical submarine cable systems while ensuring high communication quality.

Anritsu and KDDI Research continue their collaboration to increase the capacity of optical submarine cables and ensure stable international communication. (heh)

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Measurement Technology for Coherent OTDR Examine Multicore Optical Fiber for Submarine Cables in Detail

The Numbers Behind It

The Problem of Inter-Core Crosstalk

Analyze Light And Measure Optical Path Properties

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