An external modulation method is proposed and experimentally demonstrated for the generation of linearly chirped light over broadband with narrow linewidth. Our chirped light source is a combination of an optical recirculating frequency shifter loop and an optical frequency linear sweeper. A linearly chirped light over a range of 200 GHz at a chirp rate of 3.6×1016  Hz/s is generated. The instantaneous linewidth of the chirped light is estimated to be less than 50 kHz.

Broadband linearly chirped light source with narrow linewidth based on external modulation.

All-optical wavelength conversion has been demonstrated with an electroabsorption modulator based on cross-absorption modulation. For the first time, simultaneous broadcasting up to 6 different wavelengths at 10Gb/s is obtained with less than 0.5-dB polarization dependence.

All-Optical Wavelength Conversion With Multi-Channel Broadcasting at 10 Gb/s Using an Electroabsorption Modulator

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Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications XI

A novel emulator of laser Doppler frequency shift (DFS) for satellite laser communication based on microwave photonics technology is proposed and experimentally demonstrated. In order to overcome the bottleneck that the optical frequency shift signal with a wide frequency offset from near zero can hardly be obtained using traditional electro-optic or acousto-optic frequency shifting, the frequency of laser signal is first moved to a lower/higher fixed frequency and then shifted back to a higher/lower tunable frequency. The signal after cascaded frequency shifting in the opposite direction is equivalent to the original laser signal with DFS. In the experiment, the value and direction of DFS correspond to the magnitude and sign of the difference between the two frequency shifts. The DFS from −14 GHz to +14 GHz with a varying rate of 323 MHz/s is accurately implemented. In addition, the side mode suppression ratio (SMSR) of laser signals with DFS are all over 52.3 dB. The proposed scheme is significant to evaluate and test the DFS compensation capability of the satellite laser communication terminal.

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Broadband Laser Doppler Frequency Shift Emulator for Satellite Laser Communication

By using Radio-frequency (RF) driven single-sideband (SSB) modulator, precise frequency shift of single-wavelength and multi-wavelength fiber laser are both realized. Frequency shift resolution is controlled within 10MHz-20GHz and 20MHz-18GHz respectively by the RF signal.

Precise Optical Frequency Shift Based on Radio-frequency Driven Single-sideband Modulator

A method of simultaneous precise multiwavelength tuning using electrical instead of mechanical control is proposed and experimentally demonstrated. This method is achieved by using a single-side-band modulator driven by electrical radio frequency (RF) signals. It is demonstrated that the multiwavelength signals can be simultaneously tuned in frequency by an amount equal to the frequency of the RF signal. A total of 32 wavelengths with a spacing of 100 GHz (i.e., 0.8 nm at the wavelength of 1550 nm) are simultaneously tuned from 4 to 12 GHz experimentally. In principle, the tuning resolution is determined by the resolution of the RF wave generator and the line width of the light source in the system. An acceptable homogenous 20.59-dB side-band-mode suppression ratio is achieved for each wavelength output.

Precise Simultaneous Multiwavelength Tuning by Electrical RF Signals

In the modern intelligent fiber Bragg grating (FBG) sensing network, the spectrum interrogation should not only have high speed and wavelength resolution, but also use the limited spectrum resource efficiently. In this paper, we propose a spectrum interrogation technique by using a wavelength-division multiplexing (WDM) to optical time-division multiplexing (OTDM) converter, which could map the sensing signals from the wavelength domain to the time domain quickly and efficiently. The converter consists of an electro-optic switch, time delay unit and a multi-wavelength converter. The continuous WDM sensing signals are converted into pulsed WDM signals by using a 10 GHz LiNbO 3 intensity modulator as the electro-optic switch. A segment of single mode fiber (SMF) is used as the time delay unit for delaying the pulsed WDM signals overlapped in time. By using a high speed 40 GHz electro-absorption modulator (EAM) as the multi-wavelength converter, the pulsed and delayed WDM signals are converted into OTDM signals with the same wavelength. At last, the light signals after demodulation are detected by photoelectric detector (PD) which has high response speed and low cost. The mapping of the wavelength domain to the time domain in our spectrum interrogation can allocate the spectrum resource efficiently and dynamically. It is experimentally demonstrated that two signals in wavelength domain can be converted into time domain signals carried by a wavelength with a roughly equal conversion efficiency.

An efficient WDM-OTDM converter for spectrum interrogation based on nonlinear effects in electro-absorption modulator

In this paper, we propose a scheme on precisely tunable L-band multi-wavelength fiber laser. This fiber laser has two
main characteristics namely broad wavelength band, uniform power spectrum and precise electronic tunability. About 65 wavelengths output within ± 1.5dB power variation with 50GHz channel spacing in broad spectrum range can be obtained at room temperature. The measured optical signal noise ratio (OSNR) and line width of each wavelength are about 20dB and 345.5MHz respectively. Theses 65 wavelengths are able to be tuned simultaneously up or down in frequency domain with a tuning step ranging from 10 MHz to 14 GHz. The tuning resolution can potentially be as low as 1 Hz in our experiment.

Cuiqin Gao

Papers

Precise Simultaneous Multiwavelength Tuning by Electrical RF Signals

An efficient WDM-OTDM converter for spectrum interrogation based on nonlinear effects in electro-absorption modulator

Precisely tunable L-band multi-wavelength fiber laser

Multi-wavelength high repetition frequency ultrashort pulse light source