Significance  Coherent Raman scattering (CRS) is a label-free and highly specific molecular imaging technique based on four-wave mixing, which enables non-invasive and high-precision detection without damaging biological samples. It relies on two spatially and temporally synchronized tunable ultrashort laser pulses to resonantly excite chemical bonds, ensuring high specificity in identifying molecular structures. Traditional synchronously pumped optical parametric oscillators (OPOs) employ mechanical tuning, which suffers from slow speed, complex configuration and poor environmental stability, severely restricting the application of CRS in rapid dynamic and high-throughput imaging, especially in clinical emergency scenarios. Fiber optical parametric oscillators (FOPOs) feature broad tenability, excellent synchronization and high environmental robustness, making them a key light source technology for advancing CRS into clinical applications such as intraoperative rapid pathology and expanding its application scenarios to meet diverse clinical and research needs. Benefiting from the development of high-power fiber lasers and specialty fibers, FOPOs achieve ultrafast broadband tuning via electronic tuning elements, which significantly improves imaging efficiency. Their compactness and stability are further improved through photonic crystal fibers and all-fiber configurations, providing strong support for the multi-scenario application of CRS in both basic research and clinical practice. Together, these attributes establish FOPOs as a transformative platform that bridges the gap between advanced optical technology and practical biomedical utility.

Progress  FOPOs have become the core light sources for CRS imaging, with their performance being continuously optimized to meet the growing demands of biomedical and clinical applications. In terms of tuning range, FOPOs have achieved remarkable progress, enabling coverage of the ultra-broad spectral region required for coherent Raman imaging. By employing wide-range pump tuning and dispersion filtering mechanisms, state-of-the-art FOPOs cover an extremely broad wavenumber range from hundreds to several thousand cm⁻¹, encompassing both the high-wavenumber C–H stretching region and the complex fingerprint spectral region. This enables label-free comprehensive chemical detection and effective differentiation of multiple molecular components in biological samples. In terms of tuning speed, traditional OPOs rely on mechanical tuning and are relatively slow. In contrast, FOPOs achieve microsecond-level wavelength switching through advanced electronic tuning schemes. Fast tuning techniques—such as adjustable pump wavelength and repetition rate—meet the demands of real-time hyperspectral scanning in stimulated Raman scattering (SRS) and non-resonant background suppression in coherent anti-Stokes Raman scattering (CARS), greatly enhancing imaging efficiency and the ability to capture dynamic processes. This represents a paradigm shift from mechanically limited operation to electronically controlled agility, enabling video-rate spectroscopic imaging for the first time in practical settings. In terms of system integration and stability, FOPOs have evolved from traditional bulk optical configurations to more robust all-fiber architectures. Among various resonator designs, the linear cavity offers significant advantages over the ring cavity, including fewer fusion splices, lower intracavity loss, and stronger resistance to environmental disturbances, enabling turnkey long-term stable operation. These features lay a solid foundation for the practical application of CRS microscopy. Collectively, these technological advances position FOPOs as ideal light sources for high-precision, high-speed CRS imaging. They effectively promote the practical implementation and clinical translation of coherent Raman scattering techniques, providing stable, reliable, and high-chemical-specificity optical support for biomedical research and clinical diagnostics.

Conclusions and Prospects  FOPOs for coherent Raman scattering CRS imaging are advancing rapidly towards broader tuning range, faster tuning speed, higher stability, and more compact size. Over the past decade, remarkable progress has been achieved in this technology: the tuning range has been greatly expanded to cover both the fingerprint region and the high-wavenumber region; the tuning speed has been upgraded from millisecond to microsecond level; the adoption of all-fiber structures has improved system integration, facilitating its clinical applications outside the laboratory. Despite these advances, how to maintain the stability of output power, spectral purity, and pulse width during fast tuning remains a key challenge to be solved urgently. Potential solutions include integrating advanced filtering devices (such as Fabry-Perot etalon), optimizing cavity design and dispersion management, and applying intelligent control strategies based on machine learning. Looking forward, driven by new nonlinear materials, advanced integrated photonic platforms, and intelligent algorithms, FOPOs will develop towards more intelligence, multifunctionality, and modularization. They will be deeply integrated with technologies such as microfluidics and time stretching, promote the collaborative optimization of CRS imaging systems, and expand practical clinical application scenarios such as intraoperative rapid pathology and label-free quantitative monitoring. These developments will not only accelerate the clinical translation of CRS microscopy technology but also exert a profound impact in the fields of life sciences, medical diagnosis, and materials science. Furthermore, the technological breakthroughs achieved in FOPOs can provide efficient and reliable optical detection methods for precision medicine and advanced material characterization, thereby further expanding the application boundaries of CRS imaging across both biomedical and industrial domains.