In any fiber optic network, the splice closure might not be the most visible component—but it plays a critical role. Whether it’s deployed underground, aerially, or in a wall-mounted setting, its job is simple but essential: to protect and organize fiber splices while keeping out moisture, dust, and stress.

Aerial installation of fiber splice closure in real-world application

In this article, we’ll look at what makes a quality fiber optic splice closure and highlight some key performance indicators you should look for—using one of our latest models as a real-world example.

Underground fiber splice closure installation (Image source: https://bikerglen.com/blog/fort-collins-connexion-ftth-part-four/)

Image form: Glen Akins

TABLE OF CONTENTS

What Is a Fiber Optic Splice Closure?

A fiber optic splice closure is an enclosure designed to protect optical fiber splices and manage fiber routing in the field. It serves as a shield against water, dust, bending stress, and physical damage—while also providing space to organize and store spliced fibers.

Whether used in aerial installations, manholes, or wall-mounted cabinets, closures are essential in FTTx, trunk, and distribution networks.

Most fiber optic closures, regardless of form factor, share a few common internal and external components:

  • Outer housing: Usually made of high-strength plastic like ABS or PC+ABS, providing environmental and mechanical protection.

  • Cable entry ports: For incoming and outgoing fiber cables—often sealed with rubber grommets or mechanical seals.

  • Sealing system: Ensures water/dust ingress protection (IP-rated, typically IP68).

  • Splice trays: Hold and secure fiber splices, prevent stress, and maintain bend radius.

  • Fiber routing system: Guides slack fibers neatly within the enclosure to avoid micro-bending or damage.

  • Grounding parts (if metallic elements present): For lightning or surge protection in aerial installations.

 

Well-designed closures also support re-entry, allowing maintenance without damaging the fibers inside.

Dome and horizontal fiber optic splice closures side-by-side comparison

Real-World Testing: How We Validate Performance

To ensure the product performs under real-world conditions, manufacturers typically test closures against mechanical such as those outlined in ITU or IEC

At YingFeng Communication, we recently released a new model — the GJS-H048-04a, a horizontal-style closure engineered with real-world construction practices in mind. Its structure, layout, and sealing approach have been specifically optimized to address on-site usage challenges such as tight installation angles, variable weather, and re-entry needs.

To validate its durability and environmental protection, the closure underwent the following performance tests in our in-house lab:

Test Item Test Conditions Result
Airtightness Test
20 ± 2 kPa air pressure
23 ± 3 °C; fully submerged
15 minutes
No air bubbles observed during test period
Pressure Retention
20 ± 2 kPa air pressure
23 ± 3 °C
12 hours
Pressure drop ≤ 2 kPa
Impact Resistance
1 kg steel ball dropped from 1 m / 1.5 m / 2 m, 3 times at different positions
No cracks
All internal components secure
Crush Resistance
1000 N force applied over 25 cm² for 10 minutes at different angles (0° and 90° to closure axis)
No deformation
No internal loosening
Free Drop
Drop height: 75 cm
1 drop after fiber cable is pre-installed and sealed
No damage
Internal structure intact

These results show that the GJS-H048-04a not only meets common test standards, but also provides stable long-term performance under environmental stress.

Real-world mechanical impact resistance test on fiber splice closure
Airtightness pressure test on fiber optic closure

Learn More

If you’re curious about this model’s configuration or application scenarios, you can view the full product page here →, where we’ve included detailed specs, images, and contact us to downloadable datasheets.

FAQ

What is a fiber optic splice closure used for?

A splice closure is used to protect and organize fiber optic splices in the field. It provides environmental sealing and mechanical protection for fiber connections in backbone, distribution, or access networks—whether buried, aerial, or wall-mounted.

What’s the difference between dome and horizontal splice closures?

Dome (vertical) closures are typically used for large-capacity or buried applications, while horizontal (inline) closures are more compact and suitable for pole, wall, or small underground chambers. The choice depends on space constraints and fiber count.

How many fibers can a splice closure hold?

It depends on the model and number of trays. Small closures may support 12–48 cores, while larger ones can handle 144, 288, or even more. Closures like the GJS-H048-04a are designed for 48 fibers with two 24-core splice trays included.

Can a splice closure be reopened for maintenance?

Yes—most closures are designed for re-entry, allowing technicians to reopen the housing and modify or check the splices. However, proper resealing (especially for waterproof closures) is essential to maintain protection.

Are fiber splice closures waterproof?

Most quality closures are tested for IP68 protection, meaning they can resist dust and submersion in water. Airtightness and pressure-retention tests help confirm whether a closure meets waterproof performance standards. Always check test data or certifications.

Final Thoughts

Fiber optic splice closures are often overlooked—but they’re foundational to a network’s reliability. Whether you’re designing a new build or planning for field upgrades, knowing how to evaluate a closure’s sealing and impact performance can help avoid future maintenance headaches.

If you’d like to learn more about field-ready closure designs or request a sample for testing, feel free to reach out to our team. We’re always happy to share practical insights from the production line and the field.