Spatial Multiplexing, also known as Space-Division Multiplexing (SDM), is a technique used to increase the capacity of a communication or sensing system by exploiting multiple spatial channels within the same medium. Unlike other multiplexing methods such as Wavelength Division Multiplexing (WDM) or Time Division Multiplexing (TDM), which use distinct optical properties or time slots to separate signals, SDM utilizes spatial separation of channels. In the context of Fiber Bragg Grating (FBG) systems, SDM involves the use of multiple optical fibers, each containing FBG sensors, to increase the total number of sensors in the system.
Working
The core idea behind Spatial Multiplexing (SDM) is to use spatially distinct optical fibers, each functioning as an independent channel, to carry multiple signals or sensor outputs simultaneously. This approach leverages physical separation within the medium to increase sensing or communication capacity without relying on additional wavelength or time-division mechanisms within a single fiber. Here’s a detailed explanation of how SDM operates in Fiber Bragg Grating (FBG) systems:
1. Deployment of Multiple Fibers
In SDM-based FBG systems, multiple optical fibers are laid out, typically in parallel, with each fiber carrying its own set of FBG sensors. Each fiber is spatially separated, ensuring that signals from one fiber do not interfere with those in another. For example, if an application requires monitoring strain at 100 points, SDM allows the system to divide these points across several fibers, with each fiber hosting a subset of the FBG sensors.
2. Independent Sensing in Each Fiber
Each optical fiber operates independently, hosting its unique FBG sensors. The sensors within a fiber reflect specific wavelengths of light when exposed to a broadband optical source. These reflections correspond to physical parameters such as strain, temperature, or pressure at each sensor location.
3. Optical Signal Transmission
The reflected signals from the FBG sensors in each fiber are transmitted to a receiver or interrogation system. Each fiber’s reflected signal is processed separately, as the spatial separation ensures no overlap or crosstalk between fibers. The system can use identical signal processing techniques for all fibers, streamlining data acquisition.
4. Data Collection and Processing
At the interrogation unit, signals from all fibers are collected and analyzed. The interrogation unit typically includes:
In an SDM setup, the interrogation system handles data from multiple fibers in parallel, either through separate optical ports or by switching between fibers using a multiplexer.
5. Enhanced Sensing Capacity Through Spatial Multiplexing
The use of multiple fibers allows the system to multiply its sensing capacity. For instance:
Advantages of SDM in FBG Systems:
Applications of SDM in FBG Systems:
Click here to know about Photonic Crystal Fiber (PCF) Multiplexing.
Our Newsletters keep you up to date with the Photonics Industry.
By signing up for our newsletter you agree to our Terms of Service and acknowledge receipt of our Privacy Policy.
By creating an account, you agree with our Terms of Service and Privacy Policy.