Fronthaul using CPRI between BBU and RRU equipments is carried by bare fiber currently. As BBUs are more and more centralized as a pool, tremendous amount of connections may exhaust the dark fiber resource. Various optical solutions are proposed to carry CPRI. As CPRI brings stringent physical requirements, optical transmission and access technologies need to be optimized and modified.
In this paper, different optical solutions for fronthaul including OTN, passive WDM, active WDM and WDM-PON are analyzed and compared. Moreover, trials using these technologies to carry CPRI are conducted in commercial LTE environment. No worse physical performance is shown for optical solutions with more powerful OAM functions.