To address the technological bottlenecks faced by pressure measurement in high-temperature environments in aerospace， energy and chemical industries， such as severe temperature cross-sensitivity， insufficient stability of traditional electrical sensors， and the difficulty for existing optical sensors to combine high-precision measurement with mass production， this paper proposes a new solution to develop a temperature-pressure dual-parameter fiber optic Fabry-Perot sensor. By designing a silicon-based sensitive diaphragm with a central boss structure， the silicon sensing element enables simultaneous， integrated measurement of both temperature and pressure at the same point while achieving temperature decoupling. This design effectively suppresses cross-interference between temperature and pressure， enhances the accuracy of pressure measurement in complex environments and holds considerable potential for engineering applications.This work combines the fiber-optic Fabry-Perot interferometric principle with MEMS technology to design a monocrystalline silicon diaphragm featuring an internal central boss as the core sensing element. This element integrates a pressure-sensing cavity （FP1） and a temperature-sensing cavity （FP2） on the same diaphragm. The FP1 cavity is formed between the fiber end-face and the inner surface of the diaphragm， and its cavity length varies with external pressure. The FP2 cavity， on the other hand， is defined by the entire thickness of the silicon boss， making it more sensitive to temperature variations through the thermal expansion of silicon. With this monolithic design， no additional temperature reference element is required， and dual-parameter measurement is achieved at the same physical location， fundamentally avoiding the measurement error caused by spatial separation of temperature and pressure sensing elements， which is common in conventional approaches

. Based on small-deflection theory， the relationship between the central deflection of the diaphragm and the uniformly distributed pressure is analyzed. Finite element simulations are performed to optimize the geometric dimensions of the diaphragm structure， and the beneficial effect of the boss structure on improving the flatness of the central region under pressure is investigated， thereby reducing the demodulation difficulty caused by arc-shaped deformation of the interference surface. In terms of fabrication， standard MEMS processes including uniform photoresist， photolithography， development， and etching are employed for batch production of the sensitive diaphragm. After fabrication， the four-inch silicon wafer is anodically bonded to a borosilicate glass substrate， ensuring hermeticity at high temperatures. The bonded wafer is then diced into individual 4 mm × 4 mm sensing elements. CO

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laser welding is adopted to achieve all-solid-state， adhesive-free integration of the sensing element with the optical fiber， further reducing the risk of gas leakage at high temperatures caused by mismatched thermal expansion of materials. A temperature-pressure composite test platform is established to evaluate the overall performance of the integrated sensor. First， static pressure tests are performed from atmospheric pressure up to 500 kPa in steps of 100 kPa to characterize the linearity， sensitivity， hysteresis， and repeatability. Subsequently， temperature-pressure composite tests are conducted at temperature points of 22 °C， 50 °C， 100 °C， 150 °C， 200 °C， 250 °C， 300 °C， and 350 °C. During the experiments， an interrogator is used to acquire the interference spectrum in real time， and a cross-correlation demodulation algorithm is applied to accurately extract the cavity lengths of FP1 and FP2 from the composite interference spectrum. Subsequently， a temperature measurement model based on the FP2 cavity length is built， together with a compensation relationship that accounts for the temperature-induced drift

of the initial cavity length

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and the pressure sensitivity. Finally， real-time temperature decoupling of the pressure signal is achieved.The comprehensive performance of the sensor is experimentally verified over the ranges of 22 °C to 350 °C and 0 to 500 kPa. Static pressure characterization shows that the sensor exhibits excellent static characteristics： a nonlinearity error of 0.17% F.S， a hysteresis error of 0.62% F.S， a repeatability error of 0.72% F.S， and a pressure sensitivity of 0.83 nm/kPa， which is in good agreement with the design value of 0.85 nm/kPa. High-temperature tests demonstrate that the sensor can measure temperature autonomously. At 350 °C， the decoupled temperature is 349.26 °C， with a deviation of only 0.74 °C， corresponding to a temperature measurement accuracy of 0.21% F.S. Moreover， an increase in pressure sensitivity with rising temperature is observed， and a cubic polynomial relationship between sensitivity and temperature is established. After applying temperature compensation using the decoupling algorithm， the pressure measurement accuracy at high temperatures is significantly improved. Taking 350 °C as an example， the maximum measurement error is reduced to less than 1.17% F.S. The experimental data confirm that the proposed boss-type diaphragm structure can effectively separate temperature and pressure induced signals， achieve co-located dual-parameter measurement， and thereby enhance pressure measurement accuracy.This paper presents a MEMS-based fiber-optic F-P dual-parameter sensor for simultaneous temperature and pressure measurement. Through the innovative boss diaphragm design， the sensor achieves co-located dual-parameter measurement based on the deformation of a monolithic silicon sensing diaphragm under composite environments， without introducing any additional temperature sensing elements. Experimental results demonstrate that the sensor’s built-in temperature sensing and decoupling mechanism can effectively mitigate the temperature-pressure

cross-sensitivity issue in high-temperature pressure measurement. This work provides a new technical solution for accurate pressure monitoring in harsh high-temperature environments such as aero-engine hot-section components and chemical processes， holding significant application value and broad prospects for industrial adoption.