Functional Specifications Document
Functional Specification Document
Electric Field Sensors
Etch Masters:
Jonathan Young
Efrain Gutierrez
December 17, 2018
Table of Contents
Table of Contents...... 2
Introduction...... 3
Background...... 3
Product Description...... 3
Project Requirements...... 5
Point Evaluation of Customer Needs...... 5
Interpretation of Customer Needs...... 6
Analysis of Customer Needs...... 7
Project Specifications...... 7
Metrics...... 7
Analysis of Metrics...... 8
Conclusion...... 9
Introduction
This document develops the required specifications for an electric field sensor as set by the customer and design team. The design team starts with the constraints as set by the customer and evaluates them from an engineering standpoint. We itemize constraints by considering priority, time budget and engineering capabilities of our team. With this analysis we are better prepared to begin concept generation and design scheduling.
Background
In the past many electric field sensors have been created. Electric field sensors are used for characterization of high power microwaves, detect electromagnetic interference and monitor voltages at power facilities. Traditionally, these sensors are not small enough to fit in modern micro circuitry and their metallic composition perturbs the electric field they intend to measure.
The optics lab at BrighamYoungUniversity has developed electric field sensors with uniquecharacteristics. These sensors are made out of optical fiber. Fiber optic sensors have been found to have different advantages over metallic sensors made in the past. They do not perturb the electromagnetic field to be measured because they are composed of a dielectric material. Another advantage is that the reduced size of optical fiber permits the sensors to be woven inside circuitry.
Product Description
Previously, sensors are fabricated using electro-optic polymers; PMMA and DR1. Our project is to design and fabricate fiber optic electric field sensors with new polymer. The specific methods and requirements are given by the customer and outlined in the following section.
Figure 1: Block Diagram
As an Electric Field reaches into the replaced core of the fiber, the index of refraction is modified. A change in the index of refraction produces a shift in the phase of the laser going through. Therefore, the intensity of an Electric Field can be measured with the relative change in polarization of the laser from one end of the fiber to another.
Project Requirements
Point Evaluation of Customer Needs
Our project has two very specific customers; the USAF, Ipitek and our research advisors. The USAF is our funding agency and has outline specific requirements for our E-field sensor. Ipitek is a government contractor that is working in conjunction with team Etch Masters. Our research advisors, Dr. Schultz and Dr. Selfridge, employed the Etch Masters for this project, and they also have requirements for this project.
The following is a table of requirements as stated by our customers.
# / Customer Statement / Source1 / The sensor must be low loss / Ipitek, Advisors
2 / The sensor needs to be sensitive to low signals / USAF
3 / The sensor needs to be compatible with existing equipment / USAF, Ipitek, Advisors
4 / The sensor must be electrically inert / USAF
5 / Fabrication process must be repeatable / Ipitek
6 / The sensor will have high confinement / Ipitek, Advisors
7 / The sensor must be robust / USAF
8 / Testing will be simple / USAF
9 / The sensor must easy to handle and install / USAF, Advisors
10 / The sensor should be small / USAF, Advisors
11 / The sensor will be made with D-Fiber / Advisors
12 / The sensor should be calibrated. / Advisors
Figure 2: Stated Customer Needs
Interpretation of Customer Needs
We have very specific and technically minded customers. Some of their statements are very precise lending to explicit interpretation and implementation. While other statements are broad, allowing the designer a verity of implementations. In the following table we provide interpretations for the customer statement. We alsoprioritize the statements with 1 being highest and 3 being the lowest.
# / Interpretation / Priority1 / The optical signal for sensor measurement will not be significantly attenuated by the sensor or any other source. / 1
2 / The sensor should detect the Electric fields on the order of 100 V/m. / 1
3 / The end of the sensor will be fitted with a standard optical patch cord to interface with standard equipment. Measurement of the sensor will require a polarization analyzer. / 2
4 / Minimum perturbation of the Electric fields being measured. / 1
5 / The fabrication process we develop should be easy to follow and repeat at other locations. / 3
6 / The propagating Electric field will be confined to the core optical fiber and in the sensing region at least 60% of the propagating field will be confined to the redeposited polymer in the core. / 2
7 / The sensor should withstand multiple series of testing including Electric fields on the order of 10,000 V/m, or maintain sensitivity for several months, as well as withstand high temperatures. / 2
8 / A technician without a background in optics should be able to install sensor. / 3
9 / The sensor should be packaged to prevent fiber breakage. / 2
10,11 / The sensor will be fabricated in the core of a horizontal elliptical core D-fiber. The small size of optical fiber meets the size requirements; however the packaging of the fiber should not dramatically increase the size of the sensor. / 3
12 / We will model the sensors response to Electric fields. / 1
Figure 3: Interpretation of Customer Needs
Analysis of Customer Needs
Our Electric Field Sensors have several constraints. Some are more important to the success of the project than others. Our sensor must be able to measure small Electric Fields. It must be inert to these fields. The sensor should also be packaged to facilitate ease of use. It must also be compatible with existing equipment.
Project Specifications
Metrics
To measure the success of our project we have established a set of metrics to make it easier to determine how well our project meets the needs set by our customers. Each metric is assigned a reference number. The metric is also given a baseline value along with a preferred value. These metrics have also been ranked according to priority. An explanation of the values chosen follows.
Metric # / Need # / Metric / Baseline / Ideal / Rank1 / 1 / Low loss / >-20dB / >-10dB / 1
2 / 2,6 / Polarization Phase Shift / >120⁰ @ 10,000 v/m / >300⁰ @ 10,000 v/m / 2
3 / 4 / Electrically Inert / - / - / 3
4 / 12 / Sensor has been calibrated for DC and AC Electric fields. / DC: >60Mv/m AC:>60Mv/m / DC: >10Mv/m AC:>10Mv/m / 4
5 / 7 / Time Decay / >30 days / >3 months / 5
6 / 7 / Temperature Decay / >50⁰C / 60⁰C / 6
7 / 3 / Sensor fitted with a patch cord and SC connector / - / - / 7
8 / 5 / Well Documented Fabrication Process / - / - / 8
9 / 10,11 / Compactness / <3mm / <1mm / 9
10 / 8 / Tensile Strength / >1 N / >2 N / 10
11 / 8 / Breaking Curvature / 3cm diam. / 3cm diam. / 11
12 / 8 / Torsion Resistance / >3 turns / >5 turns / 12
Figure 4: Metrics
Analysis of Metrics
Metric 1: This metric is the most important because the sensitivity of the sensor depends directly on the loss of the fiber. A lower loss means better signal to noise ratio and a reduction in the input power necessary to operate.
Metric 2: This metric is ranked second because along with power loss, it affects the sensitivity directly. A 120⁰ phase shift has been achieved with other polymers such as PMMA. Therefore, the new polymer must exceed this performance.
Metric 3: Since this is one of the main breakthroughs of this type of sensor, this characteristic is ranked among the top 3 priorities. Due to the dielectric composition of this sensor, the Electric field is perturbed minimally.
Metric 4: The defined expected sensitivity should be at least 60Mv/m for both AC and DC because that is how much it was obtained with the previous polymer.
Metric 5: We assume that an operating life of 30 days is enough for this sensor to be transported and installed. This feature is ranked four because it is more important than other fabrication issues.
Metric 6: The sensor must withstand 50⁰ C assuming that the ambient temperature at any customer site will not exceed that value. Ideally the sensor should withstand 60⁰C, but not more because it can be unpoled at higher temperatures. This is one of the drawbacks of this system.
Metric 7: It is important to have a patch cord connector in order to operate the polarization analyzer and laser source. Withoutthis the system is useless. For this reason, this metric is ranked higher than the other fabrication features.
Metric 8:This metric might not be necessary to be included in the list, but the process of producing a fiber sensor is very delicate and involves many variables. Being able to reproduce the fabrication steps consistently is already a success.
Metric 9:Since the fiber must be threaded in small areas, it is crucial to have a diameter of less than 3 mm.
Metric 10:As the fiber is installed on site, it must withstand a Newton of force.
Metric 11:The fiber will bend most likely at sharp edges. Therefore it must bend at circumference of at least 3 cm of diameter.
Metric 12:Assuming the fiber will undergo twisting as it is installed, it should at least take 3 complete twists.
There are several functional specifications that must be met for our project to be a success. In specifying the metrics required for the success of our project we realize that several needs and metrics are interrelated. If we meet one metric another will follow. Metrics 1, 2, 4, 5 and 8 are all depend on the polymer deposition and the optical fiber. If we make educated and deliberate choice in type of polymer and its placement in the fiber,these metrics will be moreachievable. If we are carless with our use of polymer or blindly try different options,these metrics will not be met. Metrics 3, 6, 7, 9, 10, 11, and 12 are all dependant on the materials we use and our packaging scheme. These metrics are also of lower priority and are generally easier to meet. These metrics also depend on accomplishing the first set. It is a serial process we can not start construction of our packaging without a workable sensor.
Conclusion
To conform to all of our customer needs we will create preliminary designs to meet the metrics we have set. There are two general sets of needs, the first being a sensor that is sensitive to electric fields. The secondis that the sensor is robust enough to be used by technicians in industry. We will then create a schedule to meet the first set of metrics by a specific deadline so we have time to focus on the second set of metrics.
December 17, 2018Etch Masterspage 1