External-cavity lasers(ECLs)are widely used in optical communication systems owing to their narrow linewidths and broad wavelength-tuning ranges. However， considerable challenges remain in the development of structurally compact devices with wavelength-tuning ranges exceeding 100 nm. By optimizing the design of directional couplers within microring resonators(MRRs)and the Sagnac loop，the wavelength dependence of the external-cavity reflection spectrum is effectively suppressed. This optimization enables a broad tuning range of 135 nm spanning from 1 489 to 1 624 nm，with a simplified external-cavity configuration. A side-mode suppression ratio(SMSR)exceeding 57 dB is achieved across the entire tuning spectrum，where a peak of 67 dB is achieved at the maximum-gain wavelength of a reflective semiconductor optical amplifier(RSOA). Additionally，a maximum output power of 19. 7 mW is obtained from the laser.