This article presents, by means of computational simulation tools, a full analysis and design of an Interferometric Fiber-Optic Gyroscope (IFOG) prototype based on a closed-loop configuration with sinusoidal bias phase- modulation. The complete design of the different blocks, optical and electronic, is presented, including some novelties as the sinusoidal bias phase-modulation and the use of an integrator to generate the serrodyne phase-modulation signal. The paper includes detailed calculation of most parameter values, and the plots of the resulting signals obtained from simulation tools. The design is focused in the use of a standard single-mode optical fiber, allowing a cost competitive implementation compared to commercial IFOG, at the expense of reduced sensitivity. The design contains an IFOG model that accomplishes tactical and industrial grade applications (sensitivity ≤ 0.055 °/h). This design presents two important properties: (1) an optical subsystem with advanced conception: depolarization of the optical wave by means of Lyot depolarizers, which allows to use a sensing coil made by standard optical fiber, instead by polarization maintaining fiber, which supposes consequent cost savings and (2) a novel and simple electronic design that incorporates a linear analog integrator with reset in feedback chain, this integrator generating a serrodyne voltage-wave to apply to Phase-Modulator (PM), so that it will be obtained the interferometric phase cancellation. This particular feedback design with sawtooth-wave generated signal for a closed-loop configuration with sinusoidal bias phase modulation has not been reported till now in the scientific literature and supposes a considerable simplification with regard to previous designs based on similar configurations. The sensing coil consists of an 8 cm average diameter spool that contains 300 m of standard single-mode optical-fiber (SMF-28 type) realized by quadrupolar winding. The working wavelength will be 1310 nm. The theoretical calculated values of threshold sensitivity and dynamic range for this prototype are 0.052 °/h and 101.38 dB (from ±1.164 × 10⁻⁵ °/s up to ±78.19 °/s), respectively. The Scale-Factor (SF) non-linearity for this model is 5.404% relative to full scale, this value being obtained from data simulation results.

In this revision work, firstly classical structure and main performance parameters of interferometric fiber-optic gyroscope (IFOG) and integrated optics passive resonator gyroscope (IORG) are reviewed. Then, the main advanced models and performance parameters of these two types of rotation-rate inertial sensors are described, and finally the design trends of both types are analyzed. Taking as reference the performance parameters analyzed above, a comparative analysis between manufactured IFOG and IORG units of close geometrical dimensions is realized. This analysis leads ranking these devices into six classical levels of inertial performance: strategic grade, navigation grade, high-end tactical grade, tactical grade, industrial low-end tactical grade, and consumer grade. This classification allows to deduce the main application areas of both kinds of devices. This way, the impact of these sensors in applications such as aeronautics, aerospace navigation, mechanical micro-fabrication, tactical weapons, or, more recently, robotics can be disclosed.

In this chapter, theoretical analysis and electro-optical characterization of a fiber optic passive ring resonator interferometer (FOPRRI) were realized. First, a theoretical description and analysis of all-pass and add-drop filter configurations were performed, hence obtaining their respective transfer function, taking into account, the physical properties of a standard single-mode optical fiber as resonator constitutive material. Second, computational numerical simulations of a typical FOPRRI were performed with different analysis methods: effective index method (EIM), coupled mode theory (CMT), finite element method (FEM) and finite difference time domain (FDTD). Third, a comparative analysis of the results obtained with these methods is realized, showing the most accurate and appropriate for filter electro-optical characterization as a consequence. Last, and as an ultimate step, taking as reference the previously obtained electro-optical characterization for both configurations, the main applications are derived.

In this paper, it is shown that a suitable choice of the geometrical parameters of a silicon-wire waveguide microracetrack resonator structure can lead to a substantial improvement in the control of coupling coefficients and, hence, the design of ultracompact devices for high-performance channel add-drop filters and all-optical switching applications. On the one hand, some simple theoretical arguments and simulation results indicate that the reduction of the silicon-wire rectangular waveguide cross-section area ($\text{width}\times \text{height}$) is possible, from standard ($450\mathrm{nm}\times 220\mathrm{nm}$) to ($380\mathrm{nm}\times 200\mathrm{nm}$) on both the bus and the resonator waveguides; this action, apart from still guaranteeing a quasi-TE single-mode operation, would provide an effective improvement into scale-of-integration by a 1.30 factor per device volume. On the other hand, it will be shown by a semianalytical method (analytical calculation + numerical simulation) that achieving the waveguide-racetrack optimal coupling condition for a particular application can be reduced to a prime calculation of the main resonator geometrical parameters (bend radius, straight length, air gap and overall coupling length). In particular, the design of high-performance ultracompact waveguide-racetrack resonator structures, with pre-established $Q$ factor ($Q\ge 2000$), free spectral range ($\mathrm{FSR}\ge 15\mathrm{nm}$), full width at half-maximum ($\mathrm{FWHM}\le 5\mathrm{nm}$), finesse ($F\ge 40$) or extinction ratio signals ($\mathrm{ER}\ge 20\mathrm{dB}$) can be systematically obtained with this procedure.

A depolarized fiber optic gyroscope (DFOG) prototype with closed-loop configuration, sinusoidal-bias, and serrodyne-feedback electrooptic phase modulations was designed. A complete optoelectronic design is realized by using computational simulation tools (optical subsystem: Synopsys®-Optsim™ software and electronic subsystem: National Instruments®-MultiSim™ software). The design presented here includes both optical and electronic circuits, being the main innovation, is the use of an analogical integrator provided with reset and placed in the feedback of the electrooptic phase-modulation chain that produces a serrodyne-shaped voltage ramp signal for obtaining the interferometric signal phase cancellation. The performance obtained for this model (threshold sensitivity ≤0.052°/h; dynamic range = ± 78.19°/s) does reach the IFOG intermediate grade (tactical and industrial applications) and does demonstrate the suitability and reliability of simulation-based software tools for this kind of optoelectronic design.

Optical phase-modulation technique is a very powerful tool used in a wide variety of high performance photonic systems. Fiber-optic sensors and gyroscopes, integrated-optics sensors, or high-performance photonic integrated circuits are some examples of photonic systems where the optical phase-modulation technique can be efficiently applied. In time, such a photonic system can be integrated as the core part of some specific applications like biosensors, 5G advanced optical communication devices, gyroscopes, or high-performance computation devices. In this work, the main optical phase-modulation techniques are analyzed. Also, a study of the most significant applications of this technique is made, relating it to the most appropriate type in each case.