Fiber Splice Closure (FSC)

The invisible node — where two cables become one link, and the seal decides whether your splices survive the next decade.

A fiber splice closure (FSC) protects fusion splice points where two fiber optic cables are joined. That is its entire job — no splitters, no adapters, no cross-connects. Just a sealed enclosure that keeps water, dirt, and rodents away from the most vulnerable point in the network: the bare fusion splice.

FSCs are installed in places nobody wants to visit: up on aerial poles, inside underground manholes, buried directly in soil, or stuffed into ducts. If the seal fails, water gets in, and fusion splices degrade. There is no alarm, no warning light — just a slow increase in insertion loss that shows up as intermittent errors on the ONT, usually during rain.

Jergeo manufactures FSCs from 48 to 288 cores in PC (polycarbonate) and PP (polypropylene) shells. All models are IP68 rated — full submersion protection. Seal options include silicone rubber gaskets (PC models) and self-adhesive rubber strips (PP models), both field-resealable. Every model supports aerial, duct, and direct-burial installation. Splice trays stack vertically and slide out independently.

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JFSC-L144A Horizontal Fiber Splice Closure

JFSC-L144A Horizontal Fiber Splice Closure

Horizontal 144 ports splice closure with PC material

144 Ports IP68
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JFSC-L144B Horizontal Fiber Splice Closure

JFSC-L144B Horizontal Fiber Splice Closure

Horizontal 144 ports splice closure with 6 ports

144 Ports IP68
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JFSC-L144C Horizontal Fiber Splice Closure

JFSC-L144C Horizontal Fiber Splice Closure

Horizontal 144 ports splice closure with melt glue sealing

144 Ports IP68
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JFSC-L144E Horizontal Fiber Splice Closure

JFSC-L144E Horizontal Fiber Splice Closure

Horizontal 144 ports splice closure with self-adhesive rubber

144 Ports IP68
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JFSC-L96A Horizontal Fiber Splice Closure

JFSC-L96A Horizontal Fiber Splice Closure

Compact horizontal 96 ports splice closure

96 Ports IP68
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JFSC-T288A Vertical Fiber Splice Closure

JFSC-T288A Vertical Fiber Splice Closure

High-capacity vertical 288 ports splice closure

288 Ports IP68
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JFSC-T48A Vertical Fiber Splice Closure

JFSC-T48A Vertical Fiber Splice Closure

Compact vertical 48 ports splice closure

48 Ports IP68
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JFSC-T96A Vertical Fiber Splice Closure

JFSC-T96A Vertical Fiber Splice Closure

Vertical 96 ports splice closure for mid-capacity applications

96 Ports IP68
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Two Shapes, Two Cable Routing Strategies

Dome vs. Inline — The Shape Is Not Cosmetic, It Determines Your Installation

Fiber splice closures come in two physical configurations, and the choice is not about preference — it is about how cables enter the closure and how fibers route to the splice trays.

Dome Closure (JFSC-L series)

Cables enter from the ends of the oval/dome shell. The closure opens by removing the dome lid — the base stays mounted. This is the classic design for aerial and underground splicing where the closure is mounted to a pole, strand, or bracket.

  • More internal volume per core — more room for fiber routing and slack storage
  • Multiple inlet ports: JFSC-L144B has 3/3, JFSC-L144C and L144E have 5–6 ports for branching
  • Best for: Aerial and manhole installations where space allows, and branching configurations

Inline Closure (JFSC-T series)

Cables pass straight through the closure body in a single line. The closure opens by removing the center section or unclamping the halves. This is the design for pipeline and duct installations.

  • Slimmer cross-section — JFSC-T288A is only 121mm tall
  • Fits ducts and narrow handholes where a dome closure would not
  • Best for: Duct and pipeline installations where cross-section is the binding constraint

The practical test:

Look at where the closure will sit. If it hangs on an aerial strand or sits in a manhole with room around it, use a dome closure. If it goes inside a duct or a narrow handhole, use an inline closure. If you need to route cables in from multiple directions, the dome closure with multiple inlet ports handles the branching naturally.

Polycarbonate or Polypropylene — The Real Question Is How Many Times You Need to Open It

PC vs. PP — The Shell Material Determines Your Seal Method and Re-Entry Strategy

Two shell materials, three seal methods. The combination determines how the closure performs over its service life and what happens when a technician needs to get back in.

PC (Polycarbonate) — JFSC-L144A/B, T48A, T96A

  • Higher impact resistance. PC absorbs mechanical shock — drops, vibration on aerial poles, accidental impact — without cracking.
  • Better transparency. The translucent shell lets technicians visually inspect splice tray positions without opening the closure — a real time-saver during troubleshooting.
  • Seal method: Silicone rubber gaskets (L144A/B) or self-adhesive rubber strips (T48A/T96A).
  • Re-entry: Silicone rubber gaskets can be reused 3–5 times before losing elasticity. Self-adhesive strips need replacement each time.

Best for:

Aerial installations, frequent re-entry expected, applications where visual inspection without opening saves time.

PP (Polypropylene) — JFSC-L144C/E, L96A, T288A

  • Lighter than PC. JFSC-L96A (PP) weighs 1.3 kg vs. JFSC-T96A (PC) at 2.3 kg for the same core count.
  • Lower material cost. PP closures are typically 15–25% less expensive than PC equivalents.
  • Chemical resistance: PP resists acids, alkalis, and solvents better than PC — more durable in underground installations over 20 years.
  • Seal method: Melt glue (L144C) or self-adhesive rubber (L144E, L96A, T288A). The T288A uses PP+GF for added rigidity.
  • Caution: More brittle in cold temperatures — below -20°C, a dropped PP closure may crack where PC would only scuff.

Best for:

Underground manholes with chemical exposure, direct burial install-and-forget, high-core applications where weight matters.

Decision Matrix

Scenario Material Seal Why
Aerial, frequent re-entry PC Silicone rubber Best impact resistance, easiest reseal
Underground, chemical exposure PP Self-adhesive Better chemical resistance, lighter
Direct burial, install-and-forget PP Melt glue or self-adhesive Lowest cost, permanent seal is fine
Duct, tight space, inline PC or PP Self-adhesive Inline shape is the binding constraint
High-core (288), pipeline PP+GF Self-adhesive Rigidity at high core count, lighter

If Your Splice Closure Leaks, Nothing Else About It Matters

The Seal Is the Product — Why IP68 Is a Requirement, Not a Feature

Most field failures in fiber splice closures are seal failures, not material failures. The shell will outlast the network. The splice sleeves will outlast the shell. The seal is what fails — and when it fails, water enters the closure, corrodes the splice sleeves, and degrades the fusion splices.

IP68 vs. IP65 vs. IP67 — Why the Difference Matters

Rating Protection Level Real-World Meaning for Closures
IP65 Water jets Splash resistance only — NOT sufficient for underground or flood-prone locations
IP67 Temporary immersion (30 min at 1m) Survives brief submersion — NOT rated for standing water in manholes
IP68 Continuous submersion Full submersion protection — rated for standing water, flooding, and wet soil

All Jergeo FSCs carry IP68. This rating is achieved through three design elements:

1. Dual-seal geometry.

The cable entry ports use a two-layer seal: an inner rubber grommet that grips the cable sheath, and an outer clamp that compresses the grommet radially. This creates a seal that tightens as water pressure increases — the opposite of a simple O-ring, which can be pushed out of position by pressure differentials.

2. Seal material selection.

Silicone rubber (PC models) maintains elasticity across the full -40°C to +65°C range without hardening. Self-adhesive rubber (PP models) conforms to surface irregularities on the closure flange. Both materials are specified to maintain sealing properties for 20+ years in continuous outdoor exposure.

3. Cable entry sizing.

Every closure ships with multiple grommet sizes to match the cable diameter range. A grommet that does not match the cable diameter will not seal — this is the single most common installation error. If the cable is at the small end of the range, wrap the cable with sealing tape before inserting the grommet.

Re-entry seal integrity:

Silicone rubber gasket (JFSC-L144A/B): Inspect the gasket for cuts, nicks, or permanent deformation. If intact and still elastic, reuse it. If damaged, replace it — the gasket is a standard spare part. Re-clamp evenly, tightening opposite bolts in sequence to ensure uniform compression.

Self-adhesive rubber strip: The old strip must be completely removed and the flange cleaned before applying a new strip. Any residue creates a gap. Press the new strip firmly along the entire flange perimeter, overlapping at the ends. Takes 5–10 minutes, but skipping the cleaning step is the most common cause of re-seal failure.

Melt glue (JFSC-L144C): Heat the glue until it flows, then clamp while molten. The glue fills all surface irregularities as it cools. Most labor-intensive but creates the most robust permanent seal. Not recommended if you expect to re-enter more than once.

Frequently Asked Questions

What is the difference between a dome splice closure and an inline splice closure?
A dome closure (JFSC-L series) has an oval or dome-shaped shell where cables enter from the ends. It opens by removing the dome lid — the base stays mounted. Dome closures have more internal volume for slack storage and accept cables from multiple directions. An inline closure (JFSC-T series) has a tubular shell where cables pass straight through. It opens by unclamping the center section. Inline closures are slimmer and fit into ducts and narrow handholes where a dome closure would not. Choose dome for aerial and manhole installations where space allows. Choose inline for duct and pipeline installations where cross-section is the binding constraint.
Can a splice closure be re-entered after installation?
Yes. All Jergeo splice closures are designed for re-entry. Silicone rubber gasket seals (JFSC-L144A/B) can be resealed 3–5 times by simply re-clamping — inspect the gasket and replace if damaged. Self-adhesive rubber strip seals (most PP models and inline PC models) require the old strip to be removed, the flange cleaned, and a new strip applied — this takes 5–10 minutes per closure. Melt glue seals (JFSC-L144C) require reheating with a heat gun, which takes longer but creates a permanent seal. When re-entering, always replace splice sleeves that were disturbed and verify that all fibers maintain their routing paths and bend radii before resealing.
Why IP68 and not IP65 or IP67?
IP65 protects against water jets — splashing rain, but not submersion. IP67 protects against temporary immersion (30 minutes at 1 meter depth). IP68 protects against continuous submersion at specified depth and duration. Splice closures in underground manholes and handholes routinely sit in standing water for days after rain. Aerial closures can be submerged during flooding. Direct-burial closures are surrounded by wet soil under constant hydrostatic pressure. IP68 is the minimum rating that covers all these real-world conditions. All Jergeo FSCs are tested and rated to IP68.
How do I select the correct grommet size for my cable?
Each cable entry port on the closure has a specified diameter range (e.g., Φ7–22mm). Select the grommet that creates a snug fit on the cable sheath with no visible gap. If the cable diameter is at the small end of the range, wrap the cable with sealing tape to build up the diameter before inserting the grommet. Never use a grommet that is too large for the cable — the gap between the grommet and the cable sheath will not seal, regardless of how tightly you clamp it. This is the most common installation error that leads to water ingress.
What is the maximum number of times a splice tray can be pulled out and re-inserted?
The splice tray slides on a central post or rail. The mechanical design is rated for dozens of re-entry cycles without degradation — the tray clips and fiber routing channels do not wear out from normal use. The practical limit is not the tray mechanism but the fiber slack. Every time you pull a tray out and push it back, the fiber routing path shifts slightly. After 5–10 re-entries, the fiber slack may become disorganized, increasing the risk of micro-bends. Best practice: when re-entering a closure, take a photo of the fiber routing before you touch anything, and restore the routing to the same positions after you finish.
Can I use a 144-core closure for a 48-core cable?
Yes. You do not need to populate all splice trays. A 144-core closure with 6 trays can be installed with only 2 trays (48 cores) populated and the remaining 4 tray positions left empty. When you need to add fibers later, you install additional trays and splice sleeves. This is a common practice for phased network builds — you install the closure at full size to avoid replacing it when capacity increases, but only populate the trays you need today. The empty tray positions do not affect the seal or the IP68 rating.
What is the difference between silicone rubber and self-adhesive rubber seals?
Silicone rubber gaskets create a mechanical seal — the gasket is compressed between the closure body and the lid when the clamps are tightened. Silicone rubber maintains elasticity across a wide temperature range and can be reused 3–5 times before replacement. Self-adhesive rubber strips create an adhesive seal — the strip bonds to the flange surface and must be replaced each time the closure is opened. Self-adhesive strips are faster to install but create more waste on re-entry. For closures that will be opened frequently (e.g., in a growing network), silicone rubber gaskets are the better choice. For install-and-forget applications, self-adhesive rubber is fine.
Are Jergeo splice closures compatible with other manufacturers' splice trays?
Jergeo FSCs use standard-size splice trays (the 24-core and 36-core trays match common industry dimensions), but the tray mounting interface — the central post diameter, clip style, and slide rail — is specific to each closure model. You cannot install a third-party tray into a Jergeo closure without modifying the mounting hardware. If you need to use a specific splice tray from another manufacturer, contact us with the tray specifications and we can confirm compatibility or supply the Jergeo tray equivalent.