定义：
整个激光谐振腔包含一个周期性结构，该处发生布拉格反射的激光器。

分布反馈激光器的整个谐振腔包含一个周期性结构，作为波长的分布反射器，还包含一个增益介质。通常周期性结构的中间会发生一个相移。该结构主要是两个布拉格光栅的串联，光学增益在光栅之间。
该器件具有多个轴向谐振腔模式，考虑到损耗之后只有一个模式强度很高。（该性质与之前提到的相移有关。）因此，很容易实现单频工作，还有由于增益介质中的驻波也易于得到空间烧孔效应。
由于自由光谱区很大，因此几个纳米范围内可以无跳模的实现波长调谐。但是调谐范围没有分布布拉格反馈激光器大。 

图1：DFB光纤激光器，包含中间存在相移的光纤布拉格光栅，光栅是直接写入稀土掺杂光纤中的。 
分布反馈激光器为光纤激光器或者半导体激光器，工作在单个谐振腔模式（参阅单频工作）。如果是光纤激光器，分布反射发生在光纤布拉格光栅中，通常长度为几毫米或者厘米。
如果光纤具有很高的掺杂浓度可以实现有效的泵浦吸收，但是如果能够允许高掺杂的光纤材料（例如磷酸盐玻璃）不易于写入布拉格光栅。因此，输出功率就受到限制（例如，几十毫瓦）。
但是，这种单频光纤激光器非常简单，尺寸很小。其小尺寸和坚固性同时也得到很低的强度和相位噪声水平，即线宽很小，尽管对线宽的基本限制（Schawlow-Townes线宽）比更长的光纤激光器更高。 
半导体DFB激光器可以制作在一个集成光栅结构上，例如波纹波导。光栅结构可以在有源区的上面，但是这需要很耗时的再生长技术。一种替代方案是制作侧面耦合的结构，其中光栅在有源区的两侧。
半导体DFB激光器可以辐射不同光谱区域，至少可以辐射800 nm到2800 nm之间的光。输出功率通常为几十毫瓦。线宽为几百 MHz， 波长调谐也可以再几纳米范围。用在DWDM系统中的温度稳定装置具有很高的波长稳定性。 
DFB激光器不要与DBR激光器相混淆，后者为分布布拉格反馈激光器。

Acronym: DFB lasers

Definition: lasers where the whole laser resonator consists of a periodic structure, in which Bragg reflection occurs

More general terms: lasers

A distributed-feedback laser (DFB laser) is a laser where the whole resonator consists of a periodic structure in the laser gain medium, which acts as a distributed Bragg reflector in the wavelength range of laser action. Typically, the periodic structure is made with a phase shift in its middle. Essentially, one has a direct concatenation of two Bragg gratings with optical gain within the gratings. The device has multiple axial resonator modes, but there is typically one mode which is favored in terms of losses. (This property is related to the above-mentioned phase shift.) Therefore, single-frequency operation is often easily achieved, despite spatial hole burning due to the standing-wave pattern in the gain medium. Due to the large free spectral range, wavelength tuning without mode hops may be possible over a range of several nanometers. However, the tuning range may not be as large as for a distributed Bragg reflector laser.

Figure 1: DFB fiber laser, containing a fiber Bragg grating with a phase change in the middle, directly written into a rare-earth-doped fiber.

DFB lasers should not be confused with DBR lasers = distributed Bragg reflector lasers.

Types of DFB Lasers

Most distributed-feedback lasers are either fiber lasers or semiconductor lasers, operating on a single resonator mode (→ single-frequency operation).

Fiber Lasers

In the case of a fiber laser, the distributed reflection occurs in a fiber Bragg grating, typically with a length of a few millimeters or centimeters. Efficient pump absorption can be achieved only with a high doping concentration of the fiber, and unfortunately it is often not easy to write high contrast Bragg gratings into fibers with a composition (e.g. phosphate glass) which allows for a high doping concentration. Therefore, the output power is usually fairly limited (e.g. to a few tens of milliwatts), and the power conversion efficiency is small. However, this kind of single-frequency fiber laser is very simple and compact. Its compactness and robustness also leads to a low intensity and phase noise level, i.e., also a low linewidth, although the fundamental linewidth limit (the Schawlow–Townes linewidth) is higher than for longer fiber lasers.

Diode Lasers

Semiconductor DFB lasers can be built with an integrated grating structure, e.g. a corrugated waveguide. The grating structure may be produced on top of the active region, which however requires time-consuming regrowth techniques. An alternative is to make laterally coupled structures, where the gratings are on both sides of the active region. Semiconductor DFB lasers are available for emission in different spectral regions at least in the range from 0.8 μm to 2.8 μm.

Typical output powers are some tens of milliwatts. The linewidth is typically a few hundred MHz, and wavelength tuning is often possible over several nanometers. Temperature-stabilized devices, as used e.g. in DWDM systems, can exhibit a high wavelength stability.

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