This review concentrates on the progress and developments that have led to explosive growth in high power continuous wave (CW) fiber lasers over the last decade. Here we arbitrarily defined high power fiber operation as being close to a single mode in beam output with powers in the kilowatt range. This growth has largely been led by Yb fiber lasers up to now. However, in this review, we also highlight the potential for high power, high brightness operation of two alternative approaches, thulium fiber lasers that operate at 2 mm wavelength, and CW Raman fiber lasers (RFLs), which have yet to reach kW power levels.