Search

In this paper, a simple image rejection mixer based on the dispersion effect in the single mode fiber is proposed and experimentally demonstrated for the radio-over-fiber (RoF) system. The key idea is to control the DC bias voltages of the dual parallel Mach-Zehnder modulator (DPMZM) to compensate for the desired components and eliminate the image induced components simultaneously during the fiber transmission. The experimental results show, the image rejection ratio (IRR) of ~50 dB is realized, and the spurious free dynamic range (SFDR) is about 100.75 dB·Hz2/3. In addition, the results also demonstrate an image-free intermediate frequency (IF) range of 0.5 GHz-9.5 GHz. This image-free mixer can be widely employed in the radio-over-fiber (RoF) system, and greatly simplify the receiver structure in the base station.

In this paper, a single, flexible and stable optical frequency conversion scheme with tunable phase shift is proposed. It mainly consists of a dual-parallel binary phase shift keying (DP-BPSK) modu...

We propose and demonstrate a simple, flexible and stably operated multi-band frequency conversion approach based on a dual-polarization quadrature phase shift keying modulator (DP-QPSK). The modulator incorporating two dual parallel Mach–Zehnder modulators (DPMZMs) which perform as OFC generator and +1st carrier suppressed single sideband generator, respectively, to achieve the purpose of frequency conversion. The theoretical analysis indicates that by properly adjusting six DC bias points in the integrated modulator and two modulation indices, a frequency of received RF signal can be directly converted into different frequencies that cover different bands simultaneously. The simulation results verified the possibility. For example, the received C band frequency of 3.8 GHz can be converted into X, Ku, K and Ka bands. An X band frequency of 9.6 GHz can be down-converted to C band and up-converted to Ku, K, Ka band. In addition, the simulation also focuses on how the adjustable parameters (such as DC bias points and modulation index) influence the conversion results. It demonstrates stable conversion efficiency against the DC drafting.

A simple image rejection mixer based on a dual-polarization quadrature phase shift keying modulator is presented without a 90° hybrid coupler in electrical field. By properly adjusting DC bias points in the integrated modulator and performing balanced photo-detection, the influence of image components can be well rejected. The simulation results show that a 52.24 dB image suppression ratio (ISR) and a conversion efficiency (CE) of −9.17 dB can be achieved by the proposed mixer. Besides, another research on the ISR and CE against non-ideal parameters is carried out. According to the simulation results, it can be figured that the main factor to influence the ISR and CE is the DC drifting which results both of them changed rapidly as the DC bias points deviate from the settled values. On the other hand, with different extinction ratios and LO signal powers and RF signal powers, the mixer still performs good ISR and CE.

In this paper, a very simple multiple frequency and phase identification structure is proposed and demonstrated. The main device is a dual-parallel Mach–Zehnder modulator (DPMZM). Adjusting the DC voltages to make this modulator works at the minimum transmission point (MITP) and satisfy the power cancellation condition. Then sweeping the LO signal frequency, the frequency and phase information of the received unknown microwave signals are extracted out by the created mapping between the total output power of the system and the LO frequency. The simulation results show that the frequency measurement range can be larger than 40 GHz, the accuracy is about 4 MHz, the resolution is better than 10 MHz. In addition, it also possesses the phase identification ability with the range from 0 to π , and the accuracy can up to 0.03 rad. This approach supports an effective way to implement the multiple-frequency measurement and phase identification. It has the potential to be integrated into a receiver.

In this paper, a dual pass-band microwave photonics filter with simple, commercial structure is proposed and demonstrated. The key devices are the specially designed polarization maintaining fiber Bragg grating and the phase shift fiber Bragg grating. They are employed to extract out two orthogonally polarized sidebands and remove the undesired sideband, respectively. The simulation results show that without any extra operations or electrical processing, the dual pass-band can be achieved with the two central frequencies of 3.5 GHz and 8 GHz when the frequency spacing between the two orthogonally polarized sidebands is 12 GHz, their 3-dB bandwidth are about 500 MHz. The central frequencies of the two pass-bands can be simply tuned by adjusting the frequency spacing in a range of 4 GHz. In addition, the spurious free dynamic ranges for the two pass-bands are 75.71 dB Hz2/3 and 70.17 dB Hz2/3 respectively. Finally, a brief experiment is also carried out to demonstrate the feasibility.

In this paper, a frequency-dependent and tunable phase shifter is proposed and numerically analyzed. The key devices are the dual-polarization binary phase shift keying modulator (DP-BPSK) and the fiber Bragg grating (FBG). The phase-frequency response of the FBG is employed to determine the frequency-dependent phase shift. The simulation results show that a linear phase shift of the recovered output microwave signal which depends on the frequency of the input RF signal is achieved. In addition, by adjusting the power of the RF signal, the full range phase shift from 0° to 360° can be realized. This structure shows the spurious free dynamic range (SFDR) of 70.90 dB·Hz2/3 and 72.11 dB·Hz2/3 under different RF powers.

A multi-band frequency conversion scheme with multi-phase shift is proposed. The dual polarization quadrature phase shift keying (DP-QPSK) modulator is employed to realize multi-band frequency conversion with multi-phase shift.

A reconfigurable and stable mixer is proposed and demonstrated in this paper. It mainly consists of a dual-driven Mach–Zehnder modulator and a polarization modulator with several polarization controllers (PC) and polarizers (Pol). According to the theoretical analysis, different functions (such as single ended mixer, balanced mixer, I/Q mixer and image rejection mixer) can be realized by adjusting the PCs and Pols. The simulation results verify the possibility of multi-functions that realized by the reconfigurable mixer. In addition, another research on how the non-ideal parameters affect the image rejection ratio (ISR) and conversion efficiency of the mixer is also carried. The results show that both of them perform better as the extinction ratio gets higher. However, they are incurring a sharp decrease if the DC bias points deviate from the settled values. In the meantime, the results also indicate that the higher modulation indices lead to a better ISR. A 57.12 dB ISR can be achieved with conversion efficiency of − 9.53 dB.