A DNA analyzer (100,400), comprising: an interface for coupling a microfluidic chip (111,211,311,711,811) to the DNA analyzer (100,400), wherein the microfluidic chip (111,211,311,711,811) includes: a first domain (111a, 211a) configured for polymerase chain reaction amplification of DNA fragments, the DNA fragments being tagged with fluorescent labels; and a second domain (111b, 211b) fluidically coupled to the first domain (111a, 211a) to receive the DNA fragments, the second domain (111b, 211b) having a separation channel for electrophoretic separation of the DNA fragments; characterized in that the DNA analyzer (100,400) further comprises: - a detection module (150, 450,750) optically coupled with the microfluidic chip (111,211,311,711,811) that includes: a laser source configured to generate a laser beam; a set of optical elements configured to direct the laser beam to the separation channel to excite the fluorescent labels to emit fluorescence while the DNA fragments migrate in the separation channel, and to collect the emitted fluorescence into an optical signal; a filter module comprising an acousto-optic tunable filter (AOTF) configured to filter the optical signal to allow a first portion of the optical signal having a first wavelength to pass; based on an electrical tuning signal having a first tuning frequency, the first wavelength satisfying a matching condition of the AOTF with the first tuning frequency: and a photo-detector configured to generate an electrical detection signal in response to the filtered optical signal, and - a modulating signal generator being a low frequency modulation module configured to generate a modulation signal having a modulation frequency, and a reference signal having the modulation frequency, the modulation signal being used by the AOTF to modulate the filtered optical signal; and - a phase-sensitive detector configured to receive the reference signal and the electrical detection signal corresponding to the modulated filtered optical signal, and demodulate the electrical detection signal based on the reference signal to reduce the noise in the electrical detection signal. an interface for coupling a microfluidic chip (111,211,311,711,811) to the DNA analyzer (100,400), wherein the microfluidic chip (111,211,311,711,811) includes: a first domain (111a, 211a) configured for polymerase chain reaction amplification of DNA fragments, the DNA fragments being tagged with fluorescent labels; and a second domain (111b, 211b) fluidically coupled to the first domain (111a, 211a) to receive the DNA fragments, the second domain (111b, 211b) having a separation channel for electrophoretic separation of the DNA fragments; a first domain (111a, 211a) configured for polymerase chain reaction amplification of DNA fragments, the DNA fragments being tagged with fluorescent labels; and a second domain (111b, 211b) fluidically coupled to the first domain (111a, 211a) to receive the DNA fragments, the second domain (111b, 211b) having a separation channel for electrophoretic separation of the DNA fragments; - a detection module (150, 450,750) optically coupled with the microfluidic chip (111,211,311,711,811) that includes: a laser source configured to generate a laser beam; a set of optical elements configured to direct the laser beam to the separation channel to excite the fluorescent labels to emit fluorescence while the DNA fragments migrate in the separation channel, and to collect the emitted fluorescence into an optical signal; a filter module comprising an acousto-optic tunable filter (AOTF) configured to filter the optical signal to allow a first portion of the optical signal having a first wavelength to pass; based on an electrical tuning signal having a first tuning frequency, the first wavelength satisfying a matching condition of the AOTF with the first tuning frequency: and a photo-detector configured to generate an electrical detection signal in response to the filtered optical signal, and a laser source configured to generate a laser beam; a set of optical elements configured to direct the laser beam to the separation channel to excite the fluorescent labels to emit fluorescence while the DNA fragments migrate in the separation channel, and to collect the emitted fluorescence into an optical signal; a filter module comprising an acousto-optic tunable filter (AOTF) configured to filter the optical signal to allow a first portion of the optical signal having a first wavelength to pass; based on an electrical tuning signal having a first tuning frequency, the first wavelength satisfying a matching condition of the AOTF with the first tuning frequency: and a photo-detector configured to generate an electrical detection signal in response to the filtered optical signal, and - a modulating signal generator being a low frequency modulation module configured to generate a modulation signal having a modulation frequency, and a reference signal having the modulation frequency, the modulation signal being used by the AOTF to modulate the filtered optical signal; and - a phase-sensitive detector configured to receive the reference signal and the electrical detection signal corresponding to the modulated filtered optical signal, and demodulate the electrical detection signal based on the reference signal to reduce the noise in the electrical detection signal.