Hybrid devices

In optical fiber communication, loss and dispersion of light will occur in the transmission process, and the signal will be weakened in the long distance transmission.The traditional method is to use the optical - electric - optical relay to make up for the loss of optical signal, to extend the communication distance.Optoelectric-optical is the conversion of optical signals into electrical signals, which are amplified, processed, and then converted into optical signals, so that long-distance transmission can be achieved.But this method requires the use of optical receiver and optical transmitter, the equipment cost is high.

Photoelectric-optical amplification mode

Optical amplifiers allow optical signals to be amplified directly in the optical domain without the need to be converted into point signals, which maximizes cost savings and is easy to maintain.Therefore, it can replace the opto-electro-optical relay. There are many kinds of optical amplifiers, such as semiconductor optical amplifiers, nonlinear optical amplifiers and erbium-doped optical amplifiers.

Optical power direct amplification mode

v Erbium-doped fiber amplifier

An Erbium Doped Fiber Amplifier (EDFA) is an optical amplifier made using an optical fiber doped with a component of the rare metal erbium.In DWDM fiber communication lines, a large number of Erbium-doped fiber amplifiers are needed to improve the relayless transmission distance of signal light.

EDFA is mainly composed of 5 parts: Erbium-doped fiber (EDF), pump (pump), optical coupler (WDM), optical isolator (isolator) and optical filter (GFF).

EDFA structure: two-way pump

In order to reduce the size and cost, the three device functions in the dotted frame can be integrated into one device, called the hybrid device.

Detailed Function Introduction

Erbium-doped fiber is a kind of fiber in which a small amount of Er (Er) ions (about 25mg/kg) of rare earth elements are mixed into a 10-100m quartz fiber. It is the core of Erbium-doped fiber amplifier.To put it simply, Erbium-doped fiber, as the gain medium, plays a major role in signal light amplification.

Optical coupler is a passive optical device that mixes the input optical signal and the output light wave of the pump light source, generally using wavelength division multiplexer.

Optical isolator is a device that prevents the reflected light from affecting the stable operation of optical amplifier and ensures that optical signal can only be transmitted forward.

Gain flattening filter (GFF), also known as gain equalizing filter, is used to flatten or smooth unequal signal intensity over a specified wavelength range.This unequal signal strength usually occurs after the amplification phase.

Pumping is the process of using light to raise (or "pump") electrons from a lower energy level in an atom or molecule to a higher energy level.The pump light source in EDFA is usually a semiconductor laser with an output optical power of 10~100mw and an operating wavelength of about 980nm or 1480nm.According to the pumping mode of the pump light source, the EDFA has the same pump, the reverse pump and the bidirectional pump.

Co-direction pumping: Pump light and signal light are injected into the Erbium-doped fiber from the same end, and the pump wave and signal wave travel in the same direction

Reverse pumping: The pump light and signal light are pumped in the opposite direction, and the pump wave travels in the opposite direction of the signal wave.

Bidirectional pumping: Two pump light sources are pumped forward and backward respectively, and the pump wave and signal wave can be bidirectional.

The main reason why different pumping modes are used is that Erbium-doped fiber is injected at different stages before or after optical signal amplification, or before and after optical signal amplification. The conversion efficiency and output power of the pump light source are different, and the effect on noise performance is also different.The selection of which is mainly from the structure and characteristics of EDFA analysis, comprehensive performance key parameters and economic costs and other factors, compared to the application of EDFA in different occasions, can use different structural design.

v What are the common hybrid devices?

Hybrid Part 1: IWDM (Isolator+1550/980 WDM)

IWDM integrates polarization insensitive sensor isolator and 1550/980nm wavelength division multiplexing.

Mixed Device 2: TAIW(Tap Coupler+Isolator+1550/980 WDM)

TAIW is one of the components of the EDFA front-end solution that integrates tap-couplers, optical isolators and 1550/980nm wavelength division multiplexing capabilities.

IGFF(Isolator+Gain Flattening Filiter)

The IGFF is a mixture of an optical isolator that blocks the reverse optical input and a gain flat filter (GFF).The mixing of this device is relatively simple, adding a filter behind the optical isolator core.When the film is plated on the filter, the transmission spectrum is just complementary to the gain of the isolator core, that is, it plays the role of gain flattening.

TAP PD(TAP PhotoDiode Detector)

TAP PD component integrates a TAP coupler and a PD photodiode detector. TAP is signal diversion, and PD plays the role of photoelectric conversion. Based on its special optical design, it is easy to be integrated in the high-density optical fiber communication system to carry out online monitoring of the power of optical signals, so as to realize the power monitoring and management of optical signals.

In addition, there are Isolator+ splitter detector - ITPD(Isolator+TAP PD) and other customized components.With the increasing demand of EDFA market, network growth, PON network popularity, including the current lidar market, miniaturization, integration and CPO packaging in the later market, hybrid will have higher requirements.

At present, Hirundo can provide a full range of Hybrid device products, the functions of EDFA core five passive devices, optical Isolator (Isolator), wavelength division multiplexer (WDM), gain flat filter (GFF), Coupler (Coupler), TAP PD(splitter detector).In addition to conventional miniaturized Hybrid devices, it can also provide the size of the ultra-miniaturized Hybrid devices superior to the industry.

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