How do you measure and control the gain and noise figure of an ytterbium doped fiber amplifier?

由人工智能和领英社区提供技术支持

Ytterbium doped fiber amplifiers (YDFAs) are widely used in optical fiber communication systems, as they can boost the signal power and extend the transmission distance. However, to optimize the performance of YDFAs, you need to measure and control two key parameters: the gain and the noise figure. In this article, you will learn how to do that using different methods and tools.

此文章中的业界达人

由社区从 4 条内容中精选。了解更多

Bartosz Krawczyk

Laser Engineering PhD at Imperial College by day | Engineer of other disciplines by night

1 Gain measurement

The gain of a YDFA is the ratio of the output power to the input power of the signal. To measure the gain, you need a light source, an optical spectrum analyzer (OSA), and a variable optical attenuator (VOA). The light source generates a signal at a wavelength within the amplification range of the YDFA. The OSA measures the power spectrum of the signal before and after the YDFA. The VOA adjusts the input power to avoid saturation or underutilization of the YDFA. The gain is calculated by subtracting the input power from the output power at the same wavelength.

添加您的观点

Bartosz Krawczyk

Laser Engineering PhD at Imperial College by day | Engineer of other disciplines by night
举报内容
Gain is a ratio, so you need to divide the output power by the input power (unless you work in dB, then you can subtract the powers). Also, an OSA is not always required; a power meter is sometimes enough. A tap-port after to VOA is required to determine the input power. The gain of a YDFA amplifier also depends on pump power. Hence, in some cases one can do the a different tes: 1. Measure input power from fibre before the YDFA with an optical filter and a power meter 2. Splice the YDFA to the fibre 3. Measure power output from YDFA for different pump powers 4. Create gain curve for different pump powers

已翻译

赞

加载更多内容

2 Noise figure measurement

The noise figure of a YDFA is a measure of how much the signal-to-noise ratio (SNR) is degraded by the amplifier. To measure the noise figure, you need a light source, an OSA, a VOA, and a noise source. The noise source generates a broadband noise at a wavelength outside the amplification range of the YDFA. The light source and the noise source are combined by a coupler and fed into the YDFA. The OSA measures the power spectrum of the signal and the noise before and after the YDFA. The noise figure is calculated by using the following formula:

NF = 10 * log10[(G * Pn_out - Pn_in) / (G - 1) * Ps_in]

where G is the gain, Pn_out and Pn_in are the output and input noise powers, and Ps_in is the input signal power.

添加您的观点

3 Gain control

The gain of a YDFA can be controlled by adjusting the pump power, the input signal power, or the length of the fiber. The pump power is the amount of energy that is supplied to the YDFA by a laser diode. Increasing the pump power increases the gain, but also increases the noise and the risk of saturation. The input signal power is the amount of energy that is fed into the YDFA by the light source. Decreasing the input signal power increases the gain, but also decreases the SNR and the output power. The length of the fiber is the physical distance that the signal travels through the YDFA. Decreasing the length of the fiber decreases the gain, but also decreases the noise and the pump power consumption.

添加您的观点

Bartosz Krawczyk

Laser Engineering PhD at Imperial College by day | Engineer of other disciplines by night
举报内容
If the input power is too low and the YDFA is pumped, Q-switching behaviour can set in. This leads to a strong laser pulse due to stimulated amplified emission (ASE). This pulse can damage optical components in the system, so it should be avoided.

已翻译

赞

4 Noise figure control

The noise figure of a YDFA can be controlled by adjusting the pump power, the input signal power, or the fiber design. The pump power affects the noise figure in a similar way as the gain, as higher pump power leads to higher noise and lower noise figure. The input signal power affects the noise figure in an opposite way as the gain, as lower input signal power leads to lower noise and higher noise figure. The fiber design affects the noise figure by changing the emission and absorption cross sections of the ytterbium ions, which determine how efficiently they amplify and generate noise. The fiber design can be modified by changing the doping concentration, the core diameter, or the numerical aperture of the fiber.

添加您的观点

Bartosz Krawczyk

Laser Engineering PhD at Imperial College by day | Engineer of other disciplines by night
举报内容
To explain this section a bit more: The standard noise type for optical amplifiers in shot noise and not thermal noise (other way around for RF amplifiers); this is based on the photon wavelengths. In general, noise is amplified with each amplification stage. Hence, the noise generated at the beginning of your system dominates.

已翻译

赞

Optical Engineering

+ 关注

给文章评分

我们借助人工智能创建了此文章。您认为这篇文章怎么样？

很棒不太好

举报此文章

查看全部

How do you measure and control the gain and noise figure of an ytterbium doped fiber amplifier?

1

2

3

4

1 Gain measurement

2 Noise figure measurement

3 Gain control

4 Noise figure control

Optical Engineering

给文章评分

感谢您的反馈

更多Optical Engineering相关文章

更多相关阅读内容