Fiber Optics knowledge
- Maintained Methods of Fusion Splicer Parts
- How to Use the Fiber Optic Cleaver?
- What are Fixed Attenuators & Variable Attenuators?
- Deployable Fiber Optic Systems for Harsh Mining Environments
- Developing Miniature Fiber Optic Cable Has Become the Trend
- Fiber Optic Cleaning Procedures
- 6 Steps to Selecting a Fiber Optic Cable
- Signal Attenuation Introduction
- How Fiber Transmission Works?
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Defective products will be accepted for exchange, at our discretion, within 14 days from receipt. Buyer might be requested to return the defective products to SOPTO for verification or authorized service location, as SOPTO designated, shipping costs prepaid. .....
Fiber Optis can be used in so many fields:
Data Storage Equipment
Aerospace & Avionics
Data Transfer Tests
Oil & Gas, Imaging
Outside Plant,Central Office
Ship to Shore,Education
Unmanned Aerial Vehicles
Diagnostics & Troubleshooting
Premise Networks Carrier Networks
Independent Telecommunication Providers
- Fiber Optic Transceiver
- High Speed Cable
- Fiber Optical Cable
- Fiber Optical Patch Cords
- Splitter CWDM DWDM
- GEPON Solution
- FTTH Box ODF Closure
- PCI-E Network Card
- Network Cables
- Fiber Optical Adapter
- Fiber Optical Attenuator
- Fiber Media Converter
- PDH Multiplexers
- Protocol Converter
- Digital Video Multiplexer
- Fiber Optical Tools
Fiber Optics knowledge
Signal Attenuation Introduction
Signal attenuation in an optical fiber is measured in decibels (dB). Fiber optic cable specifications express loss as attenuation per 1 km length (dB/km). This value is multiplied by the total length of the optical fiber in kilometers to determine the fiber’s total loss in dB.
Light traveling in an optical fiber is not 100% efficient; there are several causes of signal attenuation. The loss of power also depends on the wavelength of the light and on the propagating material. For silica glass, the shorter wavelengths are attenuated the most. The lowest loss occurs at the 1550 nm wavelength, which is commonly used for long-distance transmissions.
Relationship between signal loss and light wavelength
Loss Inherent to Fiber: Light loss in a fiber that cannot be eliminated during the fabrication process is due to impurities in the glass and the absorption of light at the molecular level. Loss of light due to variations in optical density, composition, and molecular structure is called Rayleigh scattering. Rays of light encountering these variations and impurities are scattered in many directions and lost.
The absorption of light at the molecular level in fiber is mainly due to contaminants in glass such as water molecules. The ingress of water molecules into an optical fiber is one of the main factors contributing to the fiber’s increased attenuation as it ages. Silica glass’s (Si02) molecular resonance absorption also contributes to some light loss.
Loss Resulting from Fiber Fabrication: Inconsistencies in the fiber manufacturing process will result in the loss of light. For example, a 0.1% change in the core diameter can result in a 10 dB loss per kilometer. Precise tolerances must be maintained throughout the manufacturing of the fiber to minimize loss.
Splice Loss: Splice loss occurs at all splice locations. Mechanical splices usually have the highest loss, commonly ranging from 0.2 to over 1.0 dB, depending on the type of splice. Fusion splices have lower losses, usually less than 0.1 dB. A loss of 0.05 dB or less is usually achieved with good equipment and experienced personnel. High loss can be attributed to a number of factors, including:
Misaligned fiber cores
Core diameter mismatch
Connector Loss: Losses at fiber optic connectors commonly range from 0.25 to over 1.5 dB and depend greatly on the type of connector used. Other factors that contribute to the connection loss include:
Dirt or contaminants on the connector (very common)
Improper connector installation
Damaged connector faces
Misaligned fiber cores
Bend Loss: Bend loss occurs at fiber cable bends that are tighter than the cable’s minimum bend radius. Bend loss can also occur on a smaller scale from such factors as:
Sharp curves of the fiber core
Displacements of a few millimeters or less, caused by buffer or jacket imperfections
Poor installation practice
This light power loss, called microbending, can add up to a significant amount over a long distance, as much as 2dB/km for a multi-mode fiber. For example, with this level of attenuation, if light travelled over 10km of cable (without amplification), only 10% of the signal would arrive at the receiving end.
Fresnel Reflection: Fresnel reflection occurs at any light boundary where the refractive index changes, causing a portion of the incident light ray to be reflected back into the first medium. For instance, if the end of a fiber has any kind of air gap, then some of the light traveling from the air to the core, about 4%, is reflected back into the air instead of transmitting/refracting into the core. The amount being reflected can be estimated using the following formula:
Reflected Light Power at a Boundary
An index-matching material may be used in conjunction with mating connectors or with mechanical splices to reduce the reflected signal at the boundaries. The material is usually a liquid, cement (adhesive), or gel, which has an index of refraction that closely approximates that of the fiber’s core. Without the use of an index-matching material, Fresnel reflections will occur at the ends of a fiber unless there is no fiber-air interface or other significant mismatch in refractive index.
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