C-Band Gain Flattened EDFA | SIMTRUM Photonics

Features

• Gain flattening
• High gain coefficient 
• Wide spectral range

Applications

• Optical fiber communication
• Fiber optic sensing

The Erbium-doped fiber power amplifier (BA, Booster-Amplifier) is to further improve the emission power of the light source on the basis that the light source has a certain power. It is usually used to boost the power of optical signals in the range of -6dBm~+3dBm or higher. The maximum output power of ordinary single-model models can reach 26dBm (400mW), and the high-power single-model models can reach up to 40dBm (10W). It is usually used to improve the emission power of laser light sources, focusing on the pursuit of high output power. The 10-watt high-power 1550nm single-mode single-wavelength laser of SIMTRUM Optoelectronics contains a 40dBm optical power amplifier inside.

Erbium-doped fiber line amplifier (LA, In-Line Amplifier) is an optical power amplifier product specially used for line relay in fiber laser or fiber communication systems. It combines the advantages of a PA amplifier and BA amplifier and can provide high gain for small signals. Amplification can also transmit higher laser power, with the advantages of high gain, high transmit power, and relatively low noise, used between fiber segments to increase the relay length or corresponding single point to multipoint in the optical access network part to compensate for branch losses. A simple understanding can be considered as a combination of PA and BA.

2, The structure and withstand the power of the optical fiber connector are recommended for use.

The Light is incident on this interface when free-space coupling or using an optical splice to match two fibers. If the light intensity is high, it will reduce the suitability of the power and cause permanent damage to the fiber. Commonly used FC-type fiber optic connectors Use epoxy to fasten the connector ceramic ferrule to the silica fiber, The heat generated by the high-intensity light will melt the epoxy resin, which will leave a residue in the center of the fiber connector surface, which will cause the fiber connector end face to be easily damaged. And when there is pollution or dust on the end face, it is more likely to be damaged.

Estimated Optical Power Densities on Air / Glass Interface

* All values below are for unconnected (bare) silica fiber for free-space coupling to clean fiber end-faces

The output pigtails of high-power laser light sources above 200mW (or amplifiers with power above EDFA-BA-23) also have FC/APC connectors by default, but this connector is only used for power testing by users (easy to connect to a device with an FC interface). Optical power meter), as shown in the figure below.

Or if the user requires the output of the pigtail with a collimating lens, the exact parameters of the output spot (spot size, working distance, divergence angle) can be put forward, and we can match the laser with a customized fiber collimating lens accordingly. But need to increase the cost. As shown in the figure below, the Collimator and Adapter with FC/APC interface collimate the laser and output it to free space, as shown in the figure below (image source Thorlabs website).

It is necessary to emphasize to users that if the optical fiber connector outputs a laser with a power of more than 200mW, it is absolutely forbidden to use the optical fiber connector to connect with any other type of optical fiber connector, otherwise there is a great risk of damaging the optical fiber connector and the light source. If you need to connect other optical fibers, the only option is to use a fiber fusion splicer to connect by thermal fusion, as shown in the figure below.

4, There are many types of EDFA erbium-doped fiber amplifiers on the website, for example, single-wavelength EDFA, multi-wavelength EDFA, and pulsed EDFA, what is the difference between them? What are the advantages of pulsed EDFA over single wavelength EDFA?

Single-wavelength EDFA, multi-wavelength EDFA, and pulsed EDFA, although the principle is the same, are all laser-pumped erbium-doped fibers in the 980nm band to generate an optical gain in the C-band and L-band, optimized design and processing.

Single wavelength EDFA The main design of the product considers only a single wavelength signal input at the same time in the C-band or L-band and does not consider the application of simultaneous amplification of multiple wavelengths; in fact, multiple wavelengths can also be input to the amplifier at the same time, but the gain of different wavelengths in the C-band, the maximum may reach 3dB.

Multiwavelength EDFA The main design of the gain flat type product considers the simultaneous input of multiple wavelengths in the C-band at the same time, and the gain flatness of the simultaneous amplification of multiple wavelengths needs to be considered. The optimal gain flatness can be within 1.5dB by optimizing the design. However, it should be noted that the best flatness can be achieved when both the input optical power and the output optical power need to be fixed values; for example, for a certain model of multi-wavelength gain flat EDFA, the designed input optical power is -20dBm, and the input optical power is 20dBm, the gain flatness is ≤1.5dB; when the input optical power deviates from -20dBm or the output optical power deviates from 20dBm, the gain flatness may become larger;

Pulse EDFA Mainly for low repetition frequency (<1MHz), and narrow pulse width signal (<10ns), because such a pulse signal is easy to generate a high pulse when amplifying and exciting various nonlinear effects, resulting in spectral deterioration and pulse distortion, so the amplifier is in the While satisfying the power amplification, the optical nonlinear effect in the EDFA amplification process is minimized, the pulse distortion is reduced, and the signal-to-background ratio on the amplified signal spectrum is improved.

Click Here for more Single wavelength EDFA info.

5, Can a pulse-type amplifier amplify a square wave pulse and keep the pulse shape unchanged?

Although the pulsed amplifier is optimized for the pulsed laser signal, when amplifying the square-wave pulsed laser (pulse width>50ns) signal with a wider pulse width, due to the characteristics of the gain fiber, the leading edge of the signal pulse is given priority to gain the gain Amplification, the gain obtained in the middle and tail of the pulse is gradually reduced, so a square wave pulse with a flat top, after being amplified by EDFA, tends to appear in the shape of an upturned front of the pulse and a gradually reduced middle tail. This phenomenon cannot be eliminated, and the pulse The wider the width, the more obvious this phenomenon is (it can be understood that the upper-level ions consumed by the signal at the front of the pulse are not replenished in time, and the signal at the back of the pulse has already arrived, so the gain at the back of the pulse is gradually reduced). As shown in the following figure, the pulse waveform after 500ns pulse amplification and the pulse waveform after 40us pulse amplification can be seen them have top distortion, and the distortion of 40us pulse amplification is more serious.

6, What is a pump protector? How do you choose one?

We found that some customers' 980nm pump lasers encountered no light at the beginning of use or when the frequency of use was very low. During the repair, we found that part of the reason was that the end face of the output fiber was burnt (the fiber connector was plugged and unplugged when the laser was output, or the end face of the fiber had an It is caused by turning on the laser when it is dusty), and another part of the reason is that the return light enters the pump laser chip, causing irreversible damage to the chip. In view of the high frequency of this situation, it is recommended to use a pump protector. The pump protector is a fiber-coated filter element that is usually added between the pump laser and the user's WDM to prevent signals generated by rare earth fibers. A small part of the light is pumped back through the WDM, causing the pump laser to be damaged. For the convenience of use, our 980nm pump laser products can integrate a protector inside the chassis. The device transmits the pump wavelength bidirectionally (910~990nm), does not transmit the signal light of the erbium-doped fiber (anti-reflection wavelength 1500~1600nm) or does not transmit the signal light of the ytterbium-doped fiber (anti-reflection wavelength 1020~1120nm), thereby protecting the pump laser, but the protector will bring 10~15% power loss. It should be noted that the pump protector required for erbium-doped fiber and ytterbium-doped fiber is not universal, so when purchasing a pump laser, please confirm with us whether a protector is built in the pump module and the specific anti-reflection wavelength of the protector. In addition, the protector has no one-way isolation effect on the 980nm pump wavelength, that is, the 980nm laser reflected along the output fiber can still return to the pump laser through the pump protector. If the pump needs to be isolated in one direction, the 980nm isolation can be added device. The use of the pump protector is as follows:

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