Research on C-Band Light Source in Optical Communication

Abstract: This paper introduces a C-band single-pass light source structure. In the experiment, a 980nm laser diode is used as the pumping source of the light source. The maximum output power of the pigtail of the pumping source can reach 200mw, and the output center wavelength is 979.04nm. The threshold current is 27.8 mA and the maximum pump current is 450 mA. The output power of the 980 nm laser diode pigtail increases with the increase of the laser diode current, and changes substantially linearly.

1 Introduction

At present, fiber amplifiers are commonly used, and the active materials in the fibers are mainly rare earth elements such as cerium particles and cerium particles. A rare earth doped fiber amplifier can achieve a specific range of optical signal amplification. For example, erbium-doped fiber can achieve a gain of 30 nm wide around 1550 nm; erbium-doped fiber can achieve a gain bandwidth of 20-30 nm around 1310 nm. However, due to the fixed electronic structure of rare earth elements, it is difficult for such amplifiers to achieve a wider gain range (for example, covering the entire communication range S+C+L band). In order to achieve a wider communication window, a flatter gain, and a higher gain factor, the system structure needs to be improved. For example, B. O. Guan et al., using co-doping technology, in erbium-doped fiber

IJa and Bi203 are incorporated. Thereby achieving a gain bandwidth of 1554-1612 nm covering the entire L-band. YiBinLu and others used a non-linear strong double-core erbium-doped fiber to achieve a flat gain range of 105 nm and successfully covered the C+L band.

2 C-band light source

Figure 1 shows the experimental schematic diagram, using a low-concentration erbium-doped fiber single-stage single-pass C-band source experimental study.

Figure 1 Experimental design of low concentration optical fiber source

In the experiment, a 980 nm laser diode was used as the pump source. The low-concentration erbium-doped fiber is used as the gain medium. The experimental structure is a single-pass backward structure. The maximum output of the pump source pigtail output is 210row, and the center wavelength is 980.01nm. The laser diode has a threshold current of 27.82 mA and the system has a maximum pump current of 462 mA. From the test analysis, the output power of the 980 laser diode and the pump current are basically linear. The optical fiber used in the experiment came from the 46 Institute of China Electronics Technology Group. The peak absorption of the fiber reaches 4.5 dB/m, the mode field diameter is 6.68 m, and the value diameter ≥ 0.2. After many experiments and analysis and optimization, the length of the low-concentration erbium-doped fiber was 22.2m.

 Table 1 shows the relationship between laser diode pigtail power and pumping current.

Table 1： 980nm pumping current and output power relationship

Figure 2: Linear output curve of 980nm pumped laser diode output with current

In the test, three output spectra were obtained by changing the pump power. When the power is 100mw, the C-band power is 27.84mW (14.45dBm), the spectrum is not flat; the power is 120mW, and the C-band power is 30.12mW (14.79dBm). The spectrum is relatively flat; continue to increase the power. The 140 mW obtained a C-band power of 30.78 mW (15.02 dBm), but the spectrum became uneven. So to get a good flatness of the transmission ff{spectrum, the pump power must be pumped to the appropriate value. The C-band, which is not counted, has a stable performance and can be applied to the production or testing of the E-source device. It also _n should be used for applications such as fiber optic gyroscopes and long-distance fiber optic light deletion.

The test species found that if the length of the erbium-doped fiber is shorter, the pump power is smaller, and the spectrum of the output source is mainly concentrated in the long wavelength range, because when the pump power is small, the number of particles on the energy level is small. So that the particle reversal is not sufficient. The main reason for the long-wavelength is that the amplifying spontaneous emission of the short-wavelength is reabsorbed by the number of 铒 particles, so the amplified spontaneous emission of the re-emission is shifted to the long-wavelength direction, which will cause a relatively obvious peak around the wavelength of I530nm, for analysis. The reason for this peak phenomenon is that the experiment compares the forward structure and the backward structure spectrum of a relatively long fiber. It is found that if the pump power is increased to a certain value, it is found that the entire spectrum remains basically the same, and the output power is maintained. Does not increase with pump light power. During the test, the output spectrum was observed by changing the pump power, and it was found that the output power changed with the change of the pump power. When the power is taken to the appropriate value, the output spectrum will be flatter. In order to improve the output power of the output long-wave, the experimental light is taken out from the short-wavelength light wave to the optical fiber to match the long-wavelength and short-wave direction power, so that the C+L broadband band light source can be realized.

  

Figure 3: Comparison of backward and forward spectral output at the same pumping power

Three output spectra were obtained by changing the pump power during the test. When the power is 100mW, the C-band power is 27.84mW (14.45<dBm), the spectrum is not flat; the power is increased to l20mW, the C-band power is 30.2mW (14.79dBm), and the spectrum is relatively flat; continue to increase power. The C-band power is 30.78 mW (15.02 dBm) for 140 mW, but the spectrum becomes uneven. This figure illustrates the change in the ASE spectrum of the output as the pump power is gradually increased. It can be seen from Fig. 3 that the spectral characteristics of ASE vary with the power of the pump light. When the pump light power is small, the ASE spectrum is not smooth enough and can be analyzed from the green spectral line of Figure 3. When the pump light power is gradually increased, it can be observed that the spectrum becomes relatively flat, and the red spectrum line of the output spectrum can be obtained to obtain this conclusion. When the pump optical power continues to increase, the spectrum of the first half of the ASE spectrum decreases again, and the spectrum of the second half increases rapidly. Thus, although the output spectral power has a small increase, the output spectrum shows an unsmoothness, which can be obtained from the spectral line of FIG. Get this conclusion. Therefore, to obtain a smooth flat output, the pump power must be adjusted to an appropriate value. In order to reduce the loss and increase the power, the length of the erbium-doped fiber and the pump power are optimized. The final source power is 30.10mw (14.8dBm), and the power of the light source band is l526-1565nm (28.26mW). 14.5ldBm), the output spectrum is concentrated in the C-band, because the joint or the fusion will bring some loss in the experiment, so the pump light power that actually enters the erbium-doped fiber is slightly smaller than 120mW, and the C-band is erbium-doped. The 3dB bandwidth of the superfluorescent source is 31.62nm. In order to obtain a relatively flat output light, the 1530 nm wave light was flattened in the experiment, and the bandwidth after flat optimization was nearly 40 nm.

Figure 4: Light source output spectrum

3 Conclusion

Experimental design C-band light source structure. In order to provide a certain reference value for the study of wide-bandwidth light sources in the future, the main conclusions are as follows: The experiment adopts the structure of the backward C-band, which obtains the ideal light output, optimizes the concentration, length, fusion loss and pumping of the light-doped fiber. Power and other indicators, and finally get

The output power of the light source can reach 30.10mW (14.8dBm). The power source band can reach 28.26roW (14.51dBm) between 1526 and 1565nm. The studied light source can meet the requirements of fiber optic gyroscope, optoelectronic device test and signal solution. Tuning, fiber sensing and many other occasions.