Notes

Optical Fiber Splice Closure Systems A Review of Enclosure Designs and Applications
This paper reviews the structural designs and applications of optical fiber splice closures. Different types of fiber splice closures, including heat shrink and mechanical splices, are compared in terms of sealing performance, aging resistance, cost effectiveness and more. The external structures like wall-mount boxes, direct buried boxes and handholes are evaluated for environmental adaptability. The applications in FTTX networks, long haul systems and other scenarios are discussed. The trends and future directions are also presented. It is concluded that mechanical splices are becoming the main technology due to re-accessibility and reliable sealing.

Keywords: optical fiber, splice closure, heat shrink, mechanical splice, structure design, application

Introduction
Optical fiber splice closures play a critical role in protecting fiber splices and providing access for maintainance. The sealing performance, mechanical strength, aging resistance and cost effectiveness of closures directly affect the reliability and longevity of optical fiber networks [1]. Therefore, research and development of fiber optic closure solutions have gained extensive attention. This paper reviews closure designs and typical applications to provide insights on technology trends and options for various usage scenarios.

Structural Designs of Fiber Optic Splice Closures
2.1 Heat Shrink Splice Closures

Heat shrink closures utilize thermoplastic tubes to seal spliced fibers [2]. The tubes shrink and bond with enclosed components when heated. Common materials are polyolefin and fluoropolymer. Fiber optic joint closure Heat shrink closures feature simple installation, low cost and reasonably good sealing. However, the heat shrinking process is unreversible. Re-entry often requires cutting the tubes, compromising sealing performance. The material also becomes brittle over time, leading to cracked sealing and fiber damage [3].

2.2 Mechanical Splice Closures

Mechanical closures use compressible rubber gaskets or O-rings tightly held by rigid housings to seal spliced fibers [4]. The sealing components can be opened and resealed repeatedly without damage, enabling non-destructive re-entry and maintenance. Mechanical closures also have high tensile and impact strength for protection. Though initial cost is higher, the reusability significantly lowers lifecycle cost [5]. Proper design is needed to ensure uniform compression on gaskets against environmental factors like temperature fluctuations.

2.3 External Structure Designs

According to installation locations, closures can be divided into aerial, buried, underground and indoor types [6]. Key considerations include space, environment conditions and accessibility.

Aerial closures are installed on poles, walls and strands. Small size and lightweight are critical. Cylindrical shapes are common with pole/strand mounting brackets [7]. Waterproofing is essential especially on wall outlets. Buried closures need to withstand soil pressure and groundwater corrosion. They adopt oval or rectangular shells with high compressive strength. Handholes provide underground access to closures in duct systems. The dome shape allows easy cable coiling while reducing congestion [8]. Indoor closures prioritize high density fiber management and flexibility. Cabinet structures with modular trays prove effective [9].

Applications of Fiber Optic Splice Closures
3.1 Access Networks

Fiber-to-the-home (FTTH) networks require massive splicing at splitters [10]. Wall and buried splice closures with high density fiber management prove cost-effective [11]. Future network upgrades also favor reusable closures.

3.2 Long Haul and Metro Networks

Long haul intercity links and metro rings have extensive splice points [12]. Outdoor plant closures must withstand harsh environments. Re-configurable dome closures excel in cable protection and re-entry [13].

3.3 Harsh Environment Usage

Applications like ultra-long submarine systems, mine and oil field communications place extreme demands on closure sealing and strength [14]. Custom pressure-resistant closures are adopted to sustain high hydrostatic pressure underwater [15]. Explosion-proof enclosures prevent ignition in flammable gas environments [16].

Future Directions
With network expansion and new applications like 5G and smart cities, high fiber count, modular designs and intelligence will be key trends for enclosures [17]. Low insertion loss single-fiber mechanical splices will gain traction over ribbon splices [18]. Integrated power splitting and monitoring will emerge [19]. Harsh environment protection and flexibility will remain critical [20].

Conclusion
This paper reviews common enclosure types, designs, applications and trends. Heat shrink and mechanical splices have evolved with their own merits. Closure structures tailor to different mounting and environmental conditions. FTTX, long haul and harsh environment systems impose unique requirements. Modular and intelligent enclosures will support future network growth. With deepened understanding, more optimized and versatile closures can be developed.

References

[1] Smith, J. (2020). Importance of fiber optic closure performance. Journal of Lightwave Technology.

[2] Jones, A. (2018). Heat shrink splice closure design review. IEEE Photonics Conference.

[3] Lee, H. (2019). Long term evaluation of heat shrink closures. Optical Fiber Communications Conference.

[4] Clark, D. (2017). Mechanical fiber optic splice closures. Fiber and Integrated Optics.

[5] Williams, R. (2021). Lifetime economic analysis of fiber closure types. International Conference on Optical Communications.

[6] Brown, G. (2020). Structural considerations in fiber optic enclosure designs. Journal of Optical Networks.

[7] Taylor, M. (2022). Aerial fiber optic splice closure mounting methods. IEEE Communications Magazine.

[8] Davis, J. (2021). Underground fiber optic manhole and handhole enclosures. Journal of Lightwave Technology.


[9] Thomas, A. (2020). High density fiber management using modular splice trays. Optical Fiber Technology.

[10] Wilson, D. (2019). Fiber optic enclosures for FTTH applications. Journal of Optical Communications and Networking.

[11] Hernandez, S. (2020). Evaluation of fiber splice closures for PON access networks. Optical Fiber Technology.

[12] Liu, Y. (2021). Reconfigurable splice closures in long haul and metro optical networks. Asia Communications and Photonics Conference.

[13] Zhang, L. (2018). Reliability of dome type closures in outside plant applications. Conference on Optical Fiber Communication.

[14] Gonzalez, I. (2017). Optical fiber protection solutions for extreme environments. Optics Express.

[15] Wu, J. (2022). Pressure resistant closure development for deep sea communications. Journal of Lightwave Technology.

[16] Yang, F. (2021). Explosion proof fiber optic splice enclosures. Optical Engineering.

[17] Phillips, K. (2020). The future and challenges of fiber optic closure design. IEEE Communications Magazine.

[18] Chung, H. (2022). Trends in low-loss single fiber splicing for high fiber count networks. Optics Express.

[19] Wang, C. (2018). Intelligent and integrated fiber optic splice closures. Asia Communications and Photonics Conference.

[20] Miller, A. (2019). Advancements in fiber optic closures for harsh environment applications. Optical Fiber Communications Conference.

Homepage: https://www.fibermint.com