We present images and spectra of the Cepheus E ( Cep E ) region at both optical and infrared wavelengths .
Only the brightest region of the southern lobe of the Cep E outflow reveals optical emission , suggesting that the extinction close to the outflow source plays an important rôle in the observed difference between the optical and IR morphologies .
Cep E is a unique object since it provides a link between the spectroscopic properties of the optical Herbig-Haro ( HH ) objects and those of deeply embedded outflows .

The observed H _ { 2 } infrared lines allow us to determine an excitation temperature of \sim 2300 K , an Ortho-to-Para ratio of \sim 3 , and an H _ { 2 } ( 1,0 ) / ( 2,1 ) S ( 1 ) line ratio of \sim 9 .
These results are consistent with the values observed for HH objects with detected NIR emission lines , with shock excitation as the main mechanism for their formation , and also with the values observed for embedded , NIR flows .

The optical spectroscopic characteristics of Cep E ( HH 377 ) appear to be similar to the ones of low excitation HH objects .
However , the electron density determined from the [ SII ] 6731/6717 line ratio for this object ( n _ { e } = 4100 cm ^ { -3 } ) , and the [ OI ] 6300/H \alpha , [ SII ] ( 6717+6731 ) /H \alpha ratios are higher than the values of all of the previously studied low excitation HH objects .
This result is likely to be the consequence of an anomalously high environmental density in the HH 377 outflow .

The ionization fraction obtained for HH 377 is x _ { e } \sim 1 \% From this result , together with the observed [ OI ] 6300/H \alpha line ratio , we conclude that the observed H \alpha line emission is collisionally excited .
From a comparison with shock models , we also conclude that the extinction towards HH 377 is very low .
Comparing the observed H \beta and H \alpha fluxes of HH 377 with model predictions , we determine a shock speed between 15 and 20 km s ^ { -1 } , although somewhat higher velocities also produce spectra with line ratios that qualitatively agree with the observations of HH 377 .