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TH-G608N3 - Index Matching Gel, 3 cc Syringe

Fosco Connect Part No.: TH-G608N3

  • $ 78.00 or

TH-G608N3 - Index Matching Gel, 3 cc Syringe

MFG Spec Sheet

G608N3 Index Matching Gel is a crystal-clear optical coupling compound intended to reduce signal attenuation in wave guide assemblies at connections. The presence of air at the junction of two optical fibers causes significant signal refraction due to the large differential optical impedance that exists between air and the signal-carrying wave guides.

The optical coupling compound G608N3 has been formulated with the requisite optical properties of clarity, purity, and refractive index to minimize signal losses while allowing pliable mechanical connections between rigid parts. Unlike a rigid optical epoxy, this pliable gel is viscoelastic and can take up the differential thermal expansion of precision optical parts without inducing excessive stresses or delamination. Residue may be cleaned from fiber tips using methanol or isopropyl alcohol.

In many devices, these materials serve an additional function: they help seal out ambient dust or fluids from sensitive optical components. This gel is formulated to be ultraclean, non-yellowing, and unaffected by x-ray, ultraviolet or sunlight exposure. It has extremely low outgassing and volatility characteristics and is free from light-absorbing microscopic particulates. This optical product is a chemically stable, non-toxic, synthetic material with wide temperature serviceability and is suitable for designs with high reliability and long service life.

The table below gives data on the decrease in signal loss when using the gel. Each syringe comes with 3 cc of index matching gel. 

Insertion Loss Improvement
Connector Types Loss Without Index Matching Gel G608N3 Loss With Index Matching Gel G608N3 Difference
SMA-to-SMAa 2.88 dB 1.25 dB 1.63 dB
FC/PC-to-FC/PCb 1.12 dB 0.59 dB 0.53 dB
Refractive Index 402 nm 1.4995
589.3 nm 1.4646
980 nm 1.4462
1550 nm 1.4378
Refractive Index Temperature
Coefficient (25 °C to 60 °C)
-3.5 x 10-4 per °C
Refractive Index vs. Wavelength
(Cauchy Fit)a
1.4338 + 10520 λ-2
Optical Absorption (450 - 750 nm) <0.003% per µm
Apparent Viscosity (25 °C) 10,600 poises
Oil Separation (24 hrs at 100 °C) 0.2%
Evaporation (24 hrs at 100 °C) 1.0%
Specific Gravity (25 °C) 1.06
Thermal Coefficient of Expansion 0.0006 cc/cc/°C
Microscopic Particulate
10 - 34 µm <300 Particles/cc
≥35 µm 0 Particles/cc


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