Bend-insensitive fiber optic cables have become increasingly important in modern telecommunications and networking systems. These cables are designed to minimize signal loss and degradation when the fiber is bent or twisted. Here’s an guide to bend-insensitive fiber, covering its meaning, types , characteristics, applications.
What Is Bend Insensitivity?
Optical fiber is composed of a core and cladding, both crafted from glass in carrier-grade fiber optics, yet they exhibit marked distinctions. Each segment serves the purpose of capturing light within the core and facilitating its transmission to the opposite end of the fiber. Throughout this transmission, light can traverse multiple pathways, and its trajectory is contingent upon the angle of incidence at the boundary. Depending on this angle, light may either be reflected back into the core or lost into the cladding, contributing to light loss during transmission and consequent weakening of the optical signal at the receiving end.
The susceptibility of optical fibers to stress, particularly bending, poses challenges. In the case of tightly bent traditional optical fibers, some signal leakage occurs at the bend due to macrobend loss, leading to system failures and unplanned downtime. Various fiber properties determine the occurrence of this phenomenon, termed bending sensitivity. Conversely, bend insensitivity is a positive feature that provides additional robustness and simplifies the installation of multimode fiber.
What is Bend-Insensitive Fiber, and What Are Its Types?
The Fiber Optic Cable’s main challenge during deployment is that fiber optic cables are sensitive to stresses such as bending. Light from the outer core is not reflected when bent beyond the minimum bending radius.
This is why bend-insensitive fiber optic cables were invented to resist bend-related damage and minimize optical signal loss. It consists of additional layers of glass surrounding the core. This glass layer has a low index of refraction and reflects weakly guided light modes in the bends of the cable back into the core. As a result, the bend-insensitive fiber optic cable transmits light loss to a minimum, even when the cable is bent beyond the minimum bend radius.
In terms of performance, bend-insensitive fiber optic cables are much more flexible than ordinary fiber optic cables. It is usually designed to withstand up to 7500+ bending cycles. Plus, it has a much smaller bend radius, allowing it to wrap tightly or wrap around corners or equipment.
Like common fiber optic cables, there are two main types of bend-insensitive fiber: single-mode fiber (SMF) and multimode fiber (MMF).
Bend Insensitive Single Mode Fiber (BISMF)
Bend-insensitive single-mode fiber optic cable allows only one type of optical mode to pass through at any given time. The International Telecommunication Union (ITU) specifies two single-mode bend-insensitive fiber optic cable types: G.657.A and G.657.B. Let’s compare their minimum bend radius with the standard single-mode G652 fiber (30mm).
Let’s compare the minimum bend radius of G.657.1 and G.657.B with the standard single-mode G652 fiber (30 mm). The minimum bend radius of G.657.A1 Bend Insensitive Single Mode Fiber is 10 mm, while its A2 version and G.657. Single Mode Fiber has a minimum bend radius of 7.5 mm. The B2 version is more flexible and has a size of 5 mm – a difference of up to 6 times compared to normal single-mode fiber optic cables. It is for this reason that single-mode bend-insensitive fibers have great potential for long-distance, high-density, and low-installation-cost applications. It also has much lower attenuation than multimode fiber.
Bend Insensitive Multimode Fiber (BIMMF)
Bend-insensitive multimode fiber (BIMMF) incorporates an innovative core design, demonstrating a remarkable capacity to minimize macro bend loss even under the most challenging bending conditions. This inherent robustness makes bend-insensitive multimode fiber well-suited for demanding applications. The key distinction between traditional multimode fiber and BIMMF lies in the incorporation of an optical trench in the latter’s design. This trench effectively improves the fiber’s macrobend performance by retaining more of the light that would have escaped the core of a traditional multimode fiber. Consequently, when compared to standard multimode fibers, BIMMF emerges as a highly promising option for applications where loss and resistance to bending are critical. Because of their higher immunity to bending losses, without loosing performances or compatibility to other standard high bandwidth multimode fibers.
Advantages of Bend Insensitive Fibers:
Enhanced Bending Tolerance: Bend-insensitive fiber is specifically designed to withstand tight bends without significant signal loss. In contrast, regular optical fibers are more prone to signal degradation when subjected to tight bends.
Flexibility in Installation: Bend-insensitive fiber’s ability to tolerate tighter bends allows for more flexibility in cable routing and installation. This is particularly beneficial in confined spaces or applications where cables need to navigate corners. Regular optical fibers may be more challenging to install in such scenarios.
Space Efficiency: Due to its bending resilience, bend-insensitive fiber enables more compact and space-efficient installations. Regular optical fibers may require larger bend radii, limiting their suitability in environments with space constraints.
Ease of Handling: Bend-insensitive fiber is easier to handle during installation and maintenance, thanks to its reduced sensitivity to bending. Regular optical fibers may demand more careful handling to avoid signal degradation.
Versatility: Bend-insensitive fiber can be applied in various settings, including data centers, LAN/WAN networks, and telecommunications infrastructure. Its versatility makes it a suitable choice for diverse optical communication applications. Regular optical fibers may have limitations in certain bending-intensive environments.
Comparable Manufacturing Costs: Compared to normal fiber optic cables, bend-insensitive fiber optic cables are slightly more expensive, so the process is quite economical.
Compatibility: Bend-insensitive fiber is compatible with standard connectors and optical components, ensuring seamless integration into existing optical networks. Regular optical fibers may require specific considerations for compatibility in certain systems.
Compatibility With Conventional Fibers
The compatibility of bend-insensitive fiber with traditional fibers has been a focal point of discussion, addressing concerns about seamless integration and the ability to splice or connect bend-insensitive fibers with conventional ones. Rigorous modeling and testing on bend-insensitive multimode fiber (BIMMF ) have demonstrated that an optimized BIMMF is indeed backward compatible. It can be seamlessly mixed with non-BIMMF without introducing excessive loss. This means that BIMMF and regular multimode fibers (MMF) can coexist in an optical channel without complicating loss estimations. Additionally, BIMMF exhibits higher tolerance to potential misalignments when connectors are mated, providing an extra positive feature for 40 and 100 Gigabit applications.
A well-crafted BIMMF is designed to comply with all relevant industry standards, encompassing the following key points:
Full Compliance and Backward Compatibility: BIMMF OM2, OM3, and OM4 multimode fibers fully adhere to industry standards and are backward-compatible, ensuring seamless integration with existing systems.
Compatibility with 50/125um Multimode Grades: BIMMF is fully backward-compatible with the established 50/125um multimode grades, including OM2, OM3, and OM4. This compatibility allows BIMMF to be used alongside the existing installed base of multimode fibers.
Ease of Splicing and Connectorization: BIMMF can be spliced or connectorized to conventional 50/125um fiber types using commercially available equipment and established practices. No special tools or procedures are required, simplifying the integration process.
Adherence to Standards: BIMMF not only meets all relevant macrobend standards but also sets a new benchmark for bend performance. This underscores its reliability and adherence to industry specifications.
Application
Bend-insensitive fibers are well-suited for the high-density cabling requirements of data centers.
They enable efficient cable management and routing in tight spaces, contributing to a more organized and reliable data center infrastructure.
Local Area Networks (LANs) and Wide Area Networks (WANs):
In networking environments, where flexibility and ease of installation are crucial, bend-insensitive fibers prove advantageous.
They can be deployed in LANs and WANs to enhance the reliability and performance of data transmission.
Telecommunication Networks:
Bend-insensitive fibers play a vital role in telecommunication networks, where signal integrity is paramount.
They contribute to improved reliability and reduced signal loss, ensuring the seamless transmission of data over long distances.
Fiber to the x (FTTx):
In FTTx applications, bend-insensitive fibers are valuable for the last-mile connections to homes, businesses, and other end-user locations.
Their ability to withstand bending without compromising signal quality is crucial for reliable fiber optic connectivity in these scenarios.
High-Speed Internet and Broadband Networks:
With the growing demand for high-speed internet, bend-insensitive fibers support the efficient delivery of broadband services.
They contribute to minimizing signal loss, ensuring a consistent and reliable internet experience for end-users.
Security and Surveillance Systems:
In security and surveillance applications, where fiber optics are used for transmitting video and data signals over long distances, bend-insensitive fibers enhance the robustness of the communication link.
They are well-suited for installations in challenging environments where cables may need to be routed through tight spaces or around corners.
Industrial and Harsh Environments:
Bend-insensitive fibers are applicable in industrial settings where the fibers may be subjected to bending or flexing during installation or maintenance.
They provide a reliable communication solution in harsh environments, ensuring consistent performance under challenging conditions.
Emerging Technologies (5G, IoT):
As emerging technologies like 5G and the Internet of Things (IoT) continue to evolve, bend-insensitive fibers play a role in supporting the increased connectivity and data transmission demands of these technologies.
Their robust design and bending tolerance contribute to the reliability of communication in dynamic and rapidly changing environments.
Conclusion:
Bend-insensitive fiber is a key technology for optimizing the performance of fiber optic networks. Its ability to withstand tight bends and reduce signal loss makes it an essential component in modern telecommunications infrastructure. As technology continues to evolve, bend-insensitive fibers will play a crucial role in supporting higher data rates and the growing demand for flexible and reliable connectivity.
