Abstract: The study of algae is significant for monitoring marine environment and exploring biological resources. 
Confocal Raman spectroscopy has been widely used in biology as a label-free and rapid detection 
technique. Currently, the commercial micro-Raman is dominated in this field, while it is not 
applicable to field measurements for the instrumental size and the operation condition. Hence, 
a fiber optic spectrometer is introduced to develop a low-cost compact confocal-raman system 
for algae detection at ``single-cell'' level. The developed system is all-in-one designed for 
the compactness, and is well functioned with the capacities of Raman detection, microscopic 
imaging and optical tweezers capture. Four typical kinds of single-cells (Skeletonema costatum, 
N.oceanica IMET-1, Prorocentrum donghaiense Lu and Chlorella) were used to evaluate the system 
detectability, and the components such as proteins, lipids, glycogen and nucleic acids were 
recognized. Based on that, the algae cells were successfully classified into 4 species 
after using principal component analysis (PCA) method, which indicates that it is 
feasible to apply the fiber optic spectrometer for single cell analysis of marine 
microbes. It is expected that the developed system will be deployed as field instrument 
for the deck measurements in sea trials in the future.  

Key words: confocal Raman, fiber optic spectrometer, compact system, marine algae, single-cell analysis