An Analysis of the Cost-effectiveness of Optical-Technology Systems from HBM

Optical technology is becoming increasingly popular for many applications, and offers more and more advantages as the technology evolves.

FBG (Fiber Bragg Grating) sensors and interrogators provide highly accurate measurements:

For long distances (in the order of km) or very specific application scenarios (for example, high magnetic fields, intense EMI/RFI, risk of explosion, etc.).
For a large number of different types of sensors connected to a single optical fiber, reducing network and installation complexity.
In hard-to-reach locations and measurement points due to the fiber's small size and light weight.

When comparing sensors and data acquisition systems, based on optical or conventional technologies, prices on a component basis are higher. However, if you look at the full solution you'll discover that optical technology can actually be cost-effective.

Optical sensors, in particular FBG sensors, are also a good choice in terms of cost-effectiveness. At first glance it may be hard to believe, but take a second look and see how an optical technology system can save money.

The Optical Measurement Chain from Sensor to Software

HBM optical sensors and interrogators are stable and reliable during their whole life cycle.

The interrogators offer a high-channel density, making it possible to have several sensors on the same line. This reduces cable length and complexity, and simplifies installation.

As HBM offers the full measurement chain, including sensors, the DAQ system, software and accessories, it has also a complete overview of the costs involved. Let's take a look at the cost of single components as well as at the cost impact of the overall system.

1. Optical Sensors

In terms of the sensor price, optical systems tend to be more expensive than conventional sensors. So, an optical system with a high sensor count will be more expensive.

Why are optical sensors more expensive? Advantages include:

Immunity to electromagnetic noise interference (EMI)
Suitable for highly explosive atmospheres and other harsh conditions
Long-term signal stability (no drift) with an absolute zero reference
Multiplexing many and/or different sensors in a single fiber
Thinner and lightweight compared to copper cable

2. DAQ System

An optical measurement system also needs a DAQ system.

Again, the unit cost of an HBM optical DAQ system is more expensive than a conventional system. However, one single optical device can measure a greater number of sensors than a conventional one. With optical technology, you only need one new device for a greater number of sensors, which means that, at some stage, the optical solution becomes just as cost-effective.

So, instead of buying several data acquisition devices to connect a large number of sensors, you already have a high channel density to connect sensors, avoiding the need of investing in several DAQ devices.

3. Accessories

Accessories, including cables, protectors, etc., are necessary to keep all elements of a measurement system connected and the system up and running.

As optical fiber is cheaper than copper wires, so the cost advantage is clear. Cable lengths are also optimized due to the multiplexing character of optical fiber sensors.

4. System Installation

Installation also plays an important role in the overall cost. Installation time increases with the number of measurement points and time is money. Technicians, transportation, accommodation, etc., are needed, so if you compare the installation of optical sensors with electrical sensors, there is a potential ‘setting up’ investment that is higher with the optical system. However, as the number of sensors increases, the optical system becomes more appealing as individual sensor installation is faster and cable deployment is simpler.

So, if you look at break-even point, the optical solution quickly becomes the more cost-effective choice.

However, for systems with a low sensor count, the optical solution is a bit more expensive. But with an increasing number of sensors this quickly changes.

5. Special Applications

The competitiveness of an optical system becomes real for ‘special’ applications where extra protection or care is needed, for example, systems installed in ATEX areas or offshore. There are conventional and optical solutions available for use in these environments, but using a conventional system would require more effort because of the characteristics of the materials used.

Taking this into account, the origin of the break-even-point becomes closer to the origin of the graph. Again, we see that for special applications, optical technology can be cost-effective, even for a low sensor count.

The Hybrid Concept - Getting the Best of Both Worlds

No technology solves all problems and challenges in an equally perfect manner. Therefore, a hybrid concept, combining optical and conventional technology, is the best solution and HBM is one of the few suppliers in the market to offer one.

The new QuantumX MXFS BraggMETER optical interrogator has a key function regarding hybrid measurements. Being part of the QuantumX family, it brings optical and electrical technologies onto the same platform, that is, the same software, all data collected simultaneously and synchronized equipment, making it possible for engineers to choose the best available solution for each measurement.

The MXFS module is part of the QuantumX family, making it very easy for it to integrate into the electrical measurement chain. Connections via Ethernet, FireWire or Backplane are available to transfer signals. Data can be transformed as analog or as CAN signals.

All QuantumX modules, including MXFS, are compatible with catman software, making for easy analysis. In-depth knowledge of optical technology is not necessary to understand the output.

A Real Example: Cost-effectivness of an Optical Technology System

Task:

Installation of a structural health monitoring system on a 150m concrete bridge, including 35 strain measurement points, 12 triaxial accelerometers, 10 displacement sensors and 4 temperature measurements.

For the optical system, additional 35 temperature compensation sensors need to be considered for eliminating the temperature effect on the strain measurements.

Distribution of the different packages on the overall budget (click to enlarge):

Cost behavior:

When comparing the cost of each package, we clearly see the big difference in the cost of optical sensors, since the number of sensors is increased by the required temperature compensation.

However: taking the involved number of signals in account, the data acquisition system is considerably less expensive when using optical technology. The same occurs with the cost of the installation. The cost of the accessories, mainly the cables due to the distances, is also highly reduced when opting for optical technology.

Cost advantage: optical vs. conventional

For such a simple structure, a structural health monitoring system based on optical technology would be around 95% of the cost of a conventional system.

1. Sensors	371%
2. DAQ	60%
3. Accessories	40%
4. System Installation	75%
TOTAL	95%

Conclusion: Is It Worth Considering an Optical Technology System?

At first glance, optical technology seems to be more expensive than conventional technologies.

However, after taking into account every element that makes up a complete system plus the overall cost of ownership, this is no longer the case for systems with a medium to high sensor count.

Optical technology is also appealing for applications with low sensor counts in extreme environments, where the optical characteristics pose less problems and require less protection.