Selecting the correct fiber optic cable is critical for high-speed devices like the DKE30SS-M25. Using the wrong fiber is one of the most common causes of link failure—even when the connection appears physically correct. This guide explains LC-LC OM4 fiber, compares single-mode vs. multimode fiber, and provides an FAQ section to prevent common selection mistakes.
Why Fiber Selection Matters
A fiber optic link is a complete optical system consisting of:
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The optical module inside the device
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The fiber optic cable itself
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The connector and end-face quality
Mismatches in any of these can cause:
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No link light
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Failure to establish communication
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Intermittent or unstable connections
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Reduced signal quality or transmission distance
Correct fiber selection ensures reliable operation.
Optical Design of the DKE30SS-M25
The DKE30SS-M25 uses:
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LC fiber interfaces
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Multimode SR-class optical modules
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850 nm operating wavelength
This requires a cable that meets:
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Multimode fiber + LC connectors + OM4 bandwidth
Hence the official recommendation:
LC-LC OM4 multimode fiber optic cable
Performance Note: At 850 nm wavelength using OM4 fiber, the maximum transmission distance for the DKE30SS-M25 is 300 meters. Actual distance may be affected by the number of connectors, fiber quality, and total link loss.
Understanding “LC-LC OM4”
LC-LC: Connector Type
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LC (Lucent Connector) is a small-form-factor connector commonly used with SFP, SFP+, and SFP28 modules.
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Features: 1.25 mm ferrule, latch mechanism, high port density.
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"LC-LC" means LC connectors on both ends, ensuring direct compatibility with DKE30SS-M25 ports.
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Important: LC indicates the connector type only; it does not specify whether the fiber is single-mode or multimode.
OM4: Multimode Fiber Standard
OM4 is a high-bandwidth multimode fiber standard optimized for short-range, high-speed links.
| Feature | OM4 Multimode Fiber |
|---|---|
| Core / Cladding | 50/125 µm |
| Optimized Wavelength | 850 nm |
| Bandwidth | ≥ 4700 MHz·km |
| Jacket Color | Aqua |
| Typical Use | 10G / 25G / 40G / 100G short links |
OM4 ensures stable communication for SR-class optical modules with sufficient system margin for high-speed data center connections.
Single-Mode vs. Multimode Fiber
A common misconception is that single-mode fiber is "better." The truth is:
| Feature | Single-Mode (OS2) | Multimode (OM4) |
|---|---|---|
| Core Diameter | 9/125 µm | 50/125 µm |
| Optimized Wavelength | 1310 / 1550 nm | 850 nm |
| Typical Use | Long-distance, carrier networks | Short-distance, data centers |
| Cost & Power | Higher | Lower, more efficient for short links |
Single-mode fiber excels at long-distance transmission, but in short-range data center environments, multimode OM4 is the optimal choice.
FAQ: Common Fiber Selection Mistakes for DKE30SS-M25
Q1: Can LC-LC OS2 single-mode fiber be used instead of OM4?
No. The DKE30SS-M25 uses multimode SR optical modules at 850 nm. Single-mode OS2 fiber has a smaller core and mismatched wavelength, so the link will fail even if the connectors fit.
Q2: Can single-mode fiber be used if connected with FC–LC patch cords or adapters?
No. This is a common mistake. While FC–LC adapters change the connector type, they do not convert single-mode fiber into multimode fiber. Even if physically connected, the device cannot receive the optical signal, resulting in no communication.
Q3: Can SC-LC or FC-LC cables work instead of LC-LC?
Not recommended. The DKE30SS-M25 ports are LC. Using SC-LC or FC-LC introduces additional adapters. Each adapter can add approximately 0.2–0.5 dB of insertion loss and potential back-reflection, which may become a failure point in high-speed, low-margin links and reduce reliability.
Q4: Can OM3 fiber be used instead of OM4?
OM3 may work at very short distances, but OM4 provides:
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Higher bandwidth margin
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Better tolerance to loss and aging
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Greater stability in high-speed links
Therefore, OM4 is the officially recommended standard for the DKE30SS-M25.
Q5: If the connector fits, does that mean the fiber is correct?
No. Physical connection does not guarantee optical compatibility. A link only works if:
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Optical module types match (SR multimode vs. LR single-mode)
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Fiber types match (OM4 vs. OS2)
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Connector type and end-face quality are correct
How to Identify the Correct Fiber
Before installation, check:
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Cable marking: OM4 50/125 LC-LC
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Jacket color: Aqua
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Connector type: LC on both ends
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Fiber type: Multimode
Installation & Maintenance Tips:
Minimum Bend Radius: During installation, avoid tight bends. Typically, the bend radius should not be less than 10 times the cable diameter.
Dust Protection: Always install dust caps on fiber connectors when not in use.
Avoid cables labeled OS2, single-mode, SC, FC, or "universal fiber."
Quick-Check List for Link Failure Troubleshooting
If you encounter issues, follow this sequence:
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Verify Cable: Is the jacket aqua? Is it marked "OM4 50/125"?
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Check Connectors: Are both ends LC? Are the end faces clean and dust-free? (Inspect with a dedicated fiber microscope if possible.)
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Validate Equipment: Is the optical module type on the peer device also multimode SR? (Avoid mixed single-mode/multimode connections.)
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Simplify Test: Try connecting the two devices directly with a known-good, brand-new LC-LC OM4 patch cable to rule out issues with the existing cabling or adapters.
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Confirm Distance: Ensure the total fiber length is within the 300-meter maximum allowable distance.
Official Fiber Recommendation
To ensure optimal performance, use:
LC-LC OM4 multimode fiber optic cable (50/125 µm)
Using any other fiber type—even if it appears connected—may result in link failure or unstable communication.
Final Thoughts
The DKE30SS-M25 is designed for high-speed, short-range (up to 300 meters) multimode optical transmission. Correct fiber selection is key to ensuring reliable communication and avoiding downtime.
Remember: Physical Connectivity ≠ Optical Compatibility. Choose the right fiber from the start and follow installation best practices.
