## 1 Introduction  
Ultra-stable lasers are an essential instrument in the fields of time-frequency standards, precision measurements, and quantum optics [1, 2, 3, 4, 5, 6]. With the development of space technology, the application of ultra-stable lasers has expanded from ground-based experiments to space science missions [7, 8, 9, 10]. Ultra-stable laser systems on space platforms (space stations and satellites) have shown wide application prospects in space science experiments. For example, the Laser Interferometer Space Antenna (LISA) mission will use the ultra-stable laser as interferometric light source to build millions of miles of laser interferometers in space [11]. The Next Generation Gravity Mission (NGGM), based on ultra-stable lasers, will provide enhanced spatial and temporal resolution time-varying gravity field measurements [12], etc.  
Fabry-Perot (FP) cavities are the core components of ultra-stable lasers. Frequency stability of an ultra-stable laser depends on the stability of the FP cavity optical length. Compared to the laboratory ultra-stable laser, the space-borne ultra-stable laser is exposed to harsher environments, such as mechanical vibrations during rocket launch. Mechanical vibrations or shocks may cause position shift of the FP cavity, leading to a decrease in the performance of the ultra-stable laser. Therefore, improvement of the FP cavity support is a key technology in the space ultra-stable laser. Research efforts have been devoted by many research groups to address this technology [13; 14; 15]. For example, in 2020, [PERSON], [PERSON] et al. achieved transportability of a 12 cm-long FP cavity by implementing a rigid, compact, and vibration insensitive mounting [16]. In 2020, [PERSON], [PERSON] et al. mounted a FP cavity on a cubic spacer, which is rigidly mounted for both low sensitivity to environmental vibration and ability for transportation [17]. In 2021, [PERSON], [PERSON] et al. reported a transportable ultrastable laser at 1550 nm, and vibration tests were conducted including 100 km actual road transportation and 34 min continuous vibration [18]. In 2024, [PERSON], [PERSON] et al. developed a transportable laser frequency stabilization system [19], etc. In our previous works, a reliable, robust and stable method for fixing 100 mm cubic FP cavity was used to allow the cavity to pass the aerospace mechanical tests [20]. The number of support points was increased and the contact surface was enlarged to provide a reinforced-support for the cubic FP cavity. The reinforced-support method provides another choice of support method for space applications compared to the traditional four-point support method. However, in the reinforced-support design, the increase in contact surfaces and constraint points may lead to unforeseen thermo-mechanical and vibrational effects. Thus, it is necessary to investigate the effects of this reinforced-support method on the cavity performance.  
In this paper, the performance of a 100 mm cubic FP cavity with reinforced-support was analyzed. Firstly, the FP cavity with reinforced-support was modeled. Vibration sensitivity and zero-expansion temperature of the FP cavity were analyzed by the finite element analysis (FEA). Subsequently, vibration sensitivity and zero expansion temperature of the FP cavity were tested experimentally. Through compared to the traditional four-point support FP cavity, the reinforced-support FP cavity has the same vibration sensitivity. This reinforced-support FP cavity is suitable to ultra-stable lasers of \(10^{-15}\) or even \(10^{-16}\) magnitude, and may expand the application of ultra-stable lasers in transportable or space.